Two bundles in the rack and a price due Friday
One bundle came off the container with a rolled-in mark that matches nothing in the shapes tables pinned above the saw. The other is a lipped cold-formed C from a supplier whose entire catalogue is a four-page PDF with the mass column left blank. The enquiry on the desk wants a fabricated price, per tonne, back by the end of the week. Until every mark on that cutting list has a kilograms-per-metre figure beside it, there is no takeoff, no buying schedule, no galvanising booking and no quote — only a length tally, which prices nothing.
The habit of never calculating this is well earned, because for domestic hot-rolled steel the answer has always been free. Somebody put the mass into the name and then into a table, and a fabricator can go a decade reading it off rather than working it out. That arrangement holds right up to the point where the steel arrives from a mill on another continent, or is cold-formed to a profile that exists only in one manufacturer's range, or is a section cut down in your own shop from something else, or is simply lying in the yard with its paperwork lost. Then the number has to be produced rather than looked up.
What makes it worth doing carefully is that the error never behaves like noise. Every convenient simplification available — treating a rolled angle as two rectangles, treating a tapered flange as a parallel one, ignoring the lips on a cold-formed C, taking a nominal pipe wall as the wall you actually received — runs in one consistent direction for that section type, and then gets multiplied by every length of that mark in the package. A two percent lean, applied to forty tonnes, is most of a truck, and it is in your margin whichever way it points.
The designations that already answered you
Sort the cutting list before touching a caliper, because a good half of it may need no work at all. Section designations fall into two populations: the ones that state a mass and the ones that state only geometry. American rolled shapes put pounds per foot straight into the name — a W16x36 is 36 lb/ft and a C15x33.9 is 33.9 lb/ft — and UK universal and parallel-flange channel designations do the same in kilograms per metre. Angles, hollow sections, plate, pipe by nominal size and the whole IPE and HE family state dimensions only. Marking each line of the list as answered or not answered takes ten minutes and usually removes most of the measuring.
The trap sits with the marks that look familiar and are not. An angle designated L 100x100x10 is a defensible designation in at least four national systems, and the tabulated mass differs between them, because the leg lengths and thickness are the same while the heel fillet and toe radii are not. BS EN 10056-1 governs the European dimensions, JIS G 3192 governs the Japanese ones under a title that is literally dimensions, mass and permissible variations, GB/T 706 governs the Chinese hot-rolled sections and IS 808 the Indian. Reading a European table for a section rolled to one of the others is a small, quiet, entirely avoidable error — and it is the one that catches people who know the subject well enough to recognise the shape.
| Designation as written | Series and governing dimensions document | Mass in the name? |
|---|---|---|
| W16x36, C15x33.9, MC12x31, HP12x53 | US rolled shapes, ASTM A6/A6M with the AISC Manual shapes tables | Yes, the second number is pounds per foot |
| L4x4x1/2, HSS8x4x3/8, PL3/8 | Angle and plate under the same A6/A6M; HSS under ASTM A500 or A1085, which A6 does not cover | No, geometry only |
| UB 305x102x25, PFC 200x90x30 | UK sections, dimensions and masses in BS EN 10365 | Yes, the last number is kilograms per metre |
| IPE 300, HE 200 A, UPN 200 | European sections, BS EN 10365 | No, the name is a series and a depth |
| L 100x100x10 | BS EN 10056-1, or JIS G 3192, or GB/T 706, or IS 808 | No, and the four tables do not agree |
| NPS 4 Sch 40, DN 100 | ASME B36.10M for the outside diameter and wall | No, the schedule sets the wall and the wall sets the mass |
| C20015 or 200x76x20x1.5, cold-formed | The manufacturer's own catalogue, to AISI S100 or BS EN 1993-1-3 | Sometimes, and only inside that one catalogue |
Angle: the section that has never once told you its weight
An angle is named for its two legs and its thickness and nothing else, in every system there is, which makes it the shape that always needs the arithmetic. The working area is the two legs laid flat, less the heel counted twice: (leg one plus leg two, minus the thickness) multiplied by the thickness. That single subtraction is the whole subtlety, and it exists because angle legs are dimensioned to their outside faces, so the corner where they meet belongs to both legs and must be paid for once.
The answer that comes back is always low, never high. A rolled angle has a generous fillet in the heel and radiused toes, and none of that metal appears in a two-rectangle model. Because the radii are set by the rolling process rather than scaled to the section, the missing mass is a larger fraction of a 40x40x4 than of a 200x200x20 — against the EN 10056-1 tabulated masses it runs about four tenths of a percent low on the heaviest equal angles and around one and a half percent low on the lightest. On a single shelf angle over an opening it is invisible. Across a bracing package of several hundred pieces of small angle it is a line item, and it is a line item you have underpriced.
The permissible deviation of a rolled angle from its own tabulated mass is a separate matter again, and it belongs to the tolerance standard rather than to the dimension standard: BS EN 10056-2 for European angles, ASTM A6/A6M for the US series. Read the applicable table rather than carrying a remembered percentage across a border. One consolation is that unequal angles cost nothing extra to handle here, because only the sum of the legs enters the area — L150x90x12 and L90x150x12 weigh the same, which is worth knowing when a supplier quotes the legs the other way round from the drawing and everyone assumes a substitution has been made.
Two legs and a thickness are all the designation ever gives you. Turn them into kilograms per metre, and read the result as a floor rather than a figure — the fillet and the toes are extra.
The length of the first leg, measured along the outside of the angle.
The length of the second leg, measured along the outside of the angle.
The uniform thickness of both legs.
Weight per unit length
10.1 lb/ft
Geometry only, and deliberately an underestimate: the heel fillet and radiused toes are excluded, so a rolled angle weighs slightly more than this — proportionally more on light sections. Use the published shapes table when the exact catalogue weight matters.
- Cross-sectional area
- 2.97 in²
They open the calculator with your figures already in it
Steel Angle (L-Shape) Weight Calculator: 10.1 lb/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 10.1 lb/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Assumes carbon steel at 7850 kg/m³ (490 pcf), and there is no material field to say otherwise. The same L100x100x10 outline is a shade heavier in stainless and about 5.1 kg/m (3.4 lb/ft) in aluminium against 14.9 (10.0 lb/ft) — roughly a third. Weigh aluminium angle with this and every lifting, handling and fixing decision downstream is out by a factor of three.
- Galvanising puts mass back on, and it lands hardest on the light sections. A hot-dip coating runs around 600 g per square metre of surface, and an angle carries a great deal of surface for its weight: about 2 % extra on a 100x100x10, roughly double that on a 40x40x4. On a load bought and craned by weight, that is the opposite correction to the fillets and worth applying alongside them.
- The underestimate holds for a HOT-ROLLED angle and reverses for a formed one. An angle folded from plate on a press brake has no heel fillet at all, only a bend radius that takes metal out of the corner, so this figure runs marginally over rather than under. It matters most when rolled and formed sections are being compared on price by weight.
Channel: establish whether the flange is wedge-shaped before you measure anything
Channels split into two populations that behave very differently under a rectangular estimate, and the split is not by nationality but by whether the flange is parallel. European parallel flange channels, UK PFC, UPE and every plain cold-formed C have flanges of one thickness from web to toe, and modelling them as two flange rectangles plus a web rectangle is close. The American C and MC series and the older UPN do not: the inner face of the flange slopes, in the American case at roughly one in six, so the flange is thick where it meets the web and thin at the toe. One measurement cannot describe it, and which measurement you took decides whether your answer reads high or low.
Where the flange is tapered, measure at the midpoint between web and toe, which is near where the standards define the nominal thickness, and treat the result as indicative rather than as a number to quote against. On a deep channel the web reading and the toe reading can differ by a third, so the difference between a careful measurement and a careless one is not decimal places. If the section is going to be bought in quantity, this is the point at which the sensible move is to weigh a measured coupon rather than to keep refining the geometry.
Cold-formed C sections invert the problem. The steel really is one uniform thickness throughout, which makes the rectangular model unusually well behaved — but the lips are extra material the plain channel formula never sees, and on a light section those two small returns can be several percent of the whole. There is no way to recover them from a web-and-flange calculation; either add the lip legs into the tally by hand as two more strips of the same thickness, or take the mass from the manufacturer's own table, which is the honest source for a cold-formed product in any case.
Depth across the outside faces, flange width, flange thickness, web thickness. Best on parallel-flange and plain cold-formed sections, weakest where the flange is visibly wedge-shaped.
The channel's overall depth, measured across the web between the outside faces of the flanges.
The width of each flange leg, measured from the web.
The thickness of each flange.
The thickness of the web connecting the two flanges.
Weight per unit length
12.8 lb/ft
Treats web and flanges as plain rectangles. That is close for parallel-flange sections such as PFC and for plain cold-formed C-sections, and weakest for tapered-flange channels like the American C series, where the flange thins toward the toe. Fillet metal is excluded either way, so the true section weighs slightly more.
- Cross-sectional area
- 3.75 in²
They open the calculator with your figures already in it
Steel Channel (C-Shape) Weight Calculator: 12.77 lb/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 12.8 lb/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- Mass per unit length is not a grade. This page's own best case is a section measured off the steel with nothing stamped on it, and two channels of identical outline can be S235 and S355 — or merchant material folded into a channel rather than a structural section at all. That is up to a 50 per cent difference in yield strength which the four dimension fields cannot see, so matching a replacement member by weight matches its price and not its capacity.
- A channel loaded through its web twists as well as bends, because its shear centre sits outside the section behind the web — which is why channels get paired back to back, or restrained against rotation, where an I-section would not need it. Weight per unit length says nothing about that, and a purlin or trimmer picked off a weight table and left unrestrained rolls long before the steel is near its stress limit.
Pipe and tube: the wall is the entire argument
Round pipe is the one place where the name actively misleads. Nominal pipe size below NPS 14 equals neither the bore nor the outside diameter; it is a historical label that stopped matching its own dimensions generations ago and was kept because everyone already said it. What fixes the geometry is the pair of documents behind it: ASME B36.10M for welded and seamless wrought steel pipe, ASME B36.19M for the stainless dimensions. Outside diameter is constant for a nominal size, and the schedule thickens the wall inward, so a heavier schedule adds mass and takes away bore without changing anything you can measure across the outside.
The mass follows from an annulus: outside diameter squared less inside diameter squared, times pi over four, with the inside diameter being the outside less twice the wall. It is the least ambiguous of the three calculations on this page, because a round tube has no fillets, no taper and no toes — every simplification that undermines an angle or a channel estimate is simply absent. Which means that when a pipe weight comes out wrong, the geometry is not what was wrong. The wall was.
Wall thickness under-tolerance is normal, published and directional. ASTM A53/A53M, the specification most black and galvanised pipe is supplied to, permits the wall at any point to run up to 12.5 percent under nominal, so a calculation from nominal wall reads high on mass for a pipe that is entirely compliant. Structural tubing has the same character with different numbers: for HSS produced to ASTM A500 the AISC Specification for Structural Steel Buildings uses a design wall thickness of 0.93 times nominal precisely because the delivered wall runs under, while HSS to ASTM A1085 has a tightened wall tolerance and is designed at its full nominal thickness. Know which specification the tube was ordered to before deciding what the wall is, because the two answers differ by seven percent on section properties and by a similar margin on mass.
Keep the estimating question and the support question apart. For a fabrication tonnage, the pipe is the pipe. For a hanger, a trapeze, a bollard footing or a lift plan, what matters is the pipe plus its contents plus its insulation plus any flange or valve near the point of support, and a water-filled line during hydrostatic test is a different creature from the same line running dry in service. Both are legitimate uses of the same per-metre figure, and mixing them up is how a support gets sized for an empty pipe.
Outside diameter and wall, not nominal size. Run it once at nominal wall and once at the wall your specification actually permits, and you have bracketed the delivered mass.
The pipe's outer diameter.
The pipe's nominal wall thickness.
Weight per unit length
11.36 lb/ft
- Cross-sectional area
- 3.34 in²
They open the calculator with your figures already in it
Round Steel Pipe Weight Calculator: 11.36 lb/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Add the equipment this sizes
This result is a specification — 11.36 lb/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
What this calculation does not cover
- The outer diameter asked for is the pipe's measured outside diameter, not its nominal size, and the two only coincide from about 14 inches upward. Entering 101.6 mm for NPS 4 pipe, whose true outside diameter is 114.3 mm, returns 14.15 kg/m in place of 16.03 kg/m, roughly 12 per cent light, and nothing on the page can catch the substitution because 101.6 mm with a 6 mm wall is itself a perfectly valid pipe.
- The wall thickness is taken as nominal and used exactly as typed. Pipe specifications commonly permit a minus tolerance on wall, around 12.5 per cent for seamless product, so a 114.3 mm by 6 mm pipe rolled at the bottom of that tolerance weighs about 14.1 kg/m rather than 16.0. There is no corrosion allowance field either, so the figure describes the pipe as bought and not the wall left after service.
- Only the steel is weighed. The bore of a 114.3 mm by 6 mm pipe holds about 8.2 kg (18 lb) of water per metre, more than half the weight of the steel around it, and insulation, lining, external coating, flanges, valves and the water left in a line after a hydrostatic test all sit outside the number.
- This is a mass, not a capacity. Nothing here checks the pressure the wall can hold, the spacing at which the pipe may be supported, the span at which it deflects, or the stress in it during a lift. Two pipes of identical outside diameter and wall weigh the same whether they are a plain carbon grade or a high-strength line pipe grade, while their allowable pressures can differ by a factor of two.
- Density is fixed at 7,850 kg/m³ (490 pcf) and there is no material input. A stainless pipe of the same dimensions is about 1.9 per cent heavier at roughly 8,000 kg/m³ (499 pcf), and an aluminium one about a third of the figure shown, so a material substitution needs a different density.
Measuring the steel rather than the drawing
The tool decides the answer more than the technique does. A tape measure resolves to a millimetre, and a millimetre on a six-millimetre wall is a seventeen percent error before any arithmetic starts — so legs, depths and flange widths can come off a tape or a rule, but thicknesses need a vernier caliper, a micrometer, or an ultrasonic gauge where only one face is reachable. On a section that has been in the weather, add a wire brush to the list: mill scale and rust both sit proud of the steel and both go into a caliper reading as if they were metal.
Take more than one reading, and take them in places that mean something. Thickness varies along a rolled length within the mill's own tolerance, so a single measurement at a cut end — the one place the steel has been worked, burred and possibly ground — is the least representative sample available. And when the section is going to be bought in real quantity, stop measuring and weigh instead: a metre cut off the end, on a calibrated scale, settles in five minutes what an afternoon of caliper work only approximates, and it captures the fillets, the taper, the lips and the coating all at once.
- Wire-brush a clean patch on each surface you intend to measure, down to bare steel — scale and rust read as thickness and they are not.
- Take leg lengths, overall depth and flange widths to the outside faces, which is how every dimension standard defines them and how the formulas assume they were taken.
- Measure thicknesses with a caliper or micrometer, never a tape, at three points spread along the length rather than three points at one end.
- On a tapered flange, measure at the midpoint between web and toe, and note in the takeoff that the section is tapered so the next person knows why the figure is indicative.
- On a lipped cold-formed section, measure the lip return as well; it is extra steel no plain channel formula accounts for.
- Avoid cut ends, burrs, weld seams and any area that has been ground, straightened or heat-affected.
- For anything being bought by the tonne in quantity, cut a one-metre coupon, weigh it on a calibrated scale, and use that as the governing figure with the calculated value as the cross-check.
What the caliper is actually reading
Coatings sit between the jaws and the steel, and they behave in opposite directions depending on what you are trying to find out. Hot-dip galvanising to ASTM A123/A123M or ISO 1461 deposits zinc according to the coating grade tables in those standards, applied to the whole surface — so it adds real, invoiceable mass, and because it is proportional to surface area rather than to volume it matters most on exactly the light, thin, high-surface-area sections where every other correction on this page also matters most. On heavy sections it disappears into rolling tolerance; on a package of small angle bracing it does not. Galvanisers price by weight of steel delivered to them, which is a second reason to have the figure right before the material leaves the shop.
Cold-formed sections rolled from pre-galvanised coil to ASTM A653/A653M are the sharper version of the same trap. The caliper reads base metal plus a zinc layer on both faces, and both AISI S100 in North America and BS EN 1993-1-3 in Europe work from the base metal thickness, not from what the instrument saw. Take the coated reading into a mass calculation and the answer is high; take it into a capacity check and the answer is unconservative, which is the worse of the two failures. Weathered stock has the mirror-image problem: section loss from corrosion is real material gone, and on a reclaimed or long-stored section the delivered mass can sit below every published figure for that mark.
Turning kilograms per metre into a tonne on the quote
The aggregation itself is trivial and the discipline around it is not. Mass per metre multiplied by the total length of that mark, summed across marks, gives the linear steel — and the standard way to get this wrong is to take a plain average of the per-metre figures instead of one weighted by length. A package with a long run of light purlin and a handful of heavy columns has an arithmetic mean that describes no part of it. Weight the average by the share of total length each section contributes, or tally the marks separately and add the tonnes.
Then decide, explicitly and in writing, what your tonne includes beyond the linear members, because that decision is worth more than any refinement of the geometry. Connection material is the reliable offender: plates, cleats, stiffeners, gussets, base plates, bolts and weld metal are all steel, all bought, all fabricated, and all invisible to a length-times-mass tally of the main members. Drop is the other: stock arrives in fixed lengths, the cutting list does not, and the difference between the weight you buy and the weight you deliver is either in your rate or in your losses.
None of this is settled by a shapes table. How weight is measured for payment on a structural steel package is a contract matter — the AISC Code of Standard Practice for Steel Buildings and Bridges is the customary default reference in US practice, and elsewhere it is whatever the contract documents say. Establish before quoting whether the tonne being priced is bought weight or fabricated weight, whether connection material is inside the rate or measured separately, and whether coating mass is counted at all. Two estimators can price the same frame honestly and differ by five percent purely on those three answers.
| Item | Where its mass comes from | Usual treatment |
|---|---|---|
| Base plates, gussets, cleats, stiffeners | Plate area and thickness, marked off the shop drawings | Added to the tonnage as a separate plate tally |
| Bolts, nuts, washers | Supplier weight per box or per hundred | Priced as a bought item, not usually inside the tonne |
| Weld metal and consumables | Deposition rate against the weld schedule | Priced in the fabrication rate rather than the tonnage |
| Drop and offcuts | The difference between stock lengths bought and lengths delivered | Either a percentage on the buying weight or an explicit allowance |
| Galvanising or paint | Coating grade against surface area, to ASTM A123 or ISO 1461 | Charged by the coater on delivered steel weight |
| Shear studs, holding-down assemblies, grout | Product literature | Bought items, scoped in or out by the contract |
Once each mark has a per-metre figure and a total length, this closes the takeoff — but feed it a length-weighted average, and add plate and connection material separately.
The combined linear length of all steel members being tallied.
The average weight per unit length across the members being tallied.
Total steel tonnage
24.8 tons
- Total mass
- 49,591.31 lb
They open the calculator with your figures already in it
Structural Steel Tonnage Aggregator: 24.8 tons — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
Estimated cost — your price
This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.
What this calculation does not cover
- The tonnage is a takeoff, not a purchase. Sections are bought in mill or stock lengths — commonly 12 m or 40 ft — and cut to suit, so what arrives is the sum of the sticks required rather than the sum of the member lengths, and the offcut is paid for either way. On a package with many short members that gap runs to several percent before a single hole is drilled.
- A single total weight is the wrong basis for a price. Fabricated steel is quoted by weight, but the rate is set by how much work each unit of weight carries: light beams with heavy connections, copes, stiffeners and site bolts cost far more per unit of weight than the same weight in plain heavy columns. One average rate multiplied by this number misprices a light, connection-dense frame badly.
Where the estimate stops and a document starts
There comes a point on any package where a calculated mass is no longer good enough and a piece of paper has to take over. The paper is an inspection document, and in European practice the types are named in EN 10204: a 2.2 test report based on non-specific inspection, a 3.1 certificate issued by the mill's own independent inspection function, a 3.2 countersigned by an independent inspector as well. Ordering the type you need at enquiry stage costs nothing; discovering at delivery that the steel came with a 2.2 when the specification wanted a 3.1 costs a re-order. In US practice the equivalent conversation is about mill test reports and heat numbers against the material specification the shapes were ordered to.
Mass and certification are related but not the same question, and it is worth being precise about which one you are chasing. A mill certificate tells you the chemistry and the mechanical properties of the heat; it is not a weighbridge ticket. Whether you are invoiced on theoretical mass — length multiplied by the tabulated or calculated figure — or on actual weighed mass is a commercial term to settle at order stage, and for imported material where no tabulated mass exists it is the single most useful thing to agree early. On a package where the two could plausibly differ by a few percent, that agreement is worth more than any measuring you can do in the yard.
File what you used, not just what you got. Against each unfamiliar mark, record the measured dimensions, the source of the figure, whether it was calculated or weighed, and the coupon weight if you cut one. When the invoice arrives on actual weight and disagrees with the quote, or when the same section turns up on the next job, that short record is the difference between reconstructing an afternoon's work and reading one line. It is also the only honest way to answer the question that eventually gets asked about any imported section: how do you know what it weighs.
Settle these before the per-tonne rate goes out
Six things that decide a steel quote's tonnage line, none of which a shapes table will answer for an imported, cold-formed or cut-down section.
- Which marks are already answered — Split the cutting list into designations that carry a mass — US rolled shapes, UK UB and PFC — and those that carry only geometry. Measure only the second group.
- Which national table the mark belongs to — L 100x100x10 is valid under EN 10056-1, JIS G 3192, GB/T 706 and IS 808, and the tabulated masses differ because the fillet and toe radii differ.
- Measured thicknesses, not tape readings — Caliper or micrometer, three points along the length, on brushed bare steel away from cut ends and weld seams.
- The wall specification for anything hollow — ASTM A53 permits the wall up to 12.5 percent under nominal; A500 HSS is designed at 0.93 of nominal wall, A1085 at full nominal.
- A weighed coupon for anything bought in quantity — One metre on a calibrated scale captures fillets, taper, lips and coating together, and settles what caliper work only brackets.
- What the tonne includes — Plate and connection material, bolts, weld, drop and coating — inside the rate or measured separately, agreed in writing before the quote leaves.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.