The job
Modelled, not recorded. Every figure on this page is re-run through the calculator it names whenever the site is built; the estimate is worked, but no job was carried out, so the last section gives the mechanism of each likely error rather than a measured overrun.
On a vinyl plank job the carton count is the easiest figure to reach and the one that settles least. The six lines that follow it — levelling compound, primer, underlayment, spacers, transition strips and baseboard — are what turn a stack of cartons into a floor that stays flat and quiet, and each is taken from a different measurement: the floor area, the dips in the slab, the area those dips cover, the wall line, the doorways.
The job: a 15 × 20 ft (4.6 × 6.1 m) living room with a 4 × 12 ft (1.2 × 3.7 m) hallway opening off one end, the hallway's side wall running straight on from the room's, so the plan is an L with one straight 32 ft (9.75 m) wall. It sits on a concrete slab on grade. The plank is a rigid-core click vinyl, 7 × 48 in (178 × 1219 mm), with no pad on its back, laid over a separate underlayment and broken under a T-molding at the 4 ft (1.2 m) neck where the hallway leaves the room. Five doors open off the floor — front entry, kitchen, two bedrooms and a bathroom — and the old baseboard comes off and is replaced.
THE PLANK COMES FIRST BECAUSE ITS INSTRUCTION SHEET IS THE SPECIFICATION. The flatness it will tolerate decides whether the slab needs compound and where; its moisture limit decides whether the slab is ready at all; its perimeter gap decides what the baseboard has to hide; and its maximum continuous run is the figure a 32 ft (9.75 m) floor pushed through a narrow neck would have to meet, which is the reason this one is broken at the neck instead. Every later step reads one of those figures, which is why the cartons head the takeoff even though they are the last thing opened on site.
ONE QUESTION HAS NO CALCULATOR BEHIND IT, and it is named rather than guessed. Slab moisture is read with in-situ relative humidity probes to ASTM F2170, or a calcium chloride test to ASTM F1869, and judged against the plank maker's limit — nothing on this site computes the reading or the pass mark. A second question, whether 32 ft (9.75 m) of unbroken floor sits inside the plank's maximum run, is designed out rather than answered: the floating-floor guide on this site breaks an L-plan at its neck, and with that break the longest field is the room's 20 ft (6.1 m), inside every run limit this site's calculators quote, roughly 26 to 40 ft (8 to 12 m).
WHAT THIS PAGE IS. Every quantity comes from the calculator linked at its step, on the inputs shown; the few figures worked from those by hand — the bag counts, the allowance on the pour, the carton and roll rounding, the casing widths — show their arithmetic in the text. Nothing was laid. The last section is where this estimate is likely to be wrong and in which direction — mechanism, not a measured overrun.
What was measured, and how
Living room and hallway at floor level
15 × 20 ft (4.57 × 6.10 m) plus 4 × 12 ft (1.22 × 3.66 m): 348 sq ft (32.33 m²), ordered as one quantity
Taped wall to wall at the floor in both directions, with the hallway taken from the living room's wall line to its end wall. Starting the hallway at a door frame or at the room's corner either loses the strip where the two spaces meet or counts it twice, and that error lands on every line worked from area.
The wall line, and the openings in it
94 ft (28.65 m) of outline; doorways of 36, 36, 30, 30 and 28 in (914, 914, 762, 762 and 711 mm), averaging 32 in (813 mm); 80 ft 8 in (24.59 m) of wall once they are out; casings 2 1/4 in (57 mm) wide; the neck 48 in (1219 mm) between the hallway walls
The outline walked wall by wall, then each doorway measured between the jambs at floor level, where the transition strip will sit, with the casing width noted. Reading the size off the door leaf, or forgetting the casing the baseboard stops against, carries the error into three lines at once: spacers, strips and baseboard.
The run of each field, with the neck broken
20 ft (6.10 m) in the room and 12 ft (3.66 m) in the hallway along the plank direction; 15 ft (4.57 m) across the room; 32 ft (9.75 m) through the junction if it were left unbroken
Taken along the plank direction in each field: from the room's far wall to the line of its end wall, where the hallway opens and the break sits, and from that line on to the hallway's end wall. Taped straight through the junction it reads 32 ft (9.75 m), a figure that would count only if the floor floated as one piece; putting the break anywhere but on that line leaves a stub of one field inside the other and shifts both lengths.
Slab flatness, read on a grid
One dish of about 8 × 10 ft (2.44 × 3.05 m), 80 sq ft (7.43 m²), down to about 1/2 in (13 mm) and averaging 1/4 in (6.35 mm); the rest inside the tolerance
One laser line set for the whole floor and a depth written down at every point of a 3 ft (0.9 m) grid, then a straightedge over any reading that looks out of place, all judged against the plank's printed tolerance — commonly on the order of 1/8 in under 6.5 ft (3 mm under 2 m). Sizing the pour from its lowest reading would buy compound for a depth only one spot has, and a shallow bowl reads as flat to the eye until the numbers are on paper.
Slab moisture, tested before anything is ordered
Read against the plank maker's printed limit; no calculator on this site computes the reading or the pass mark
Holes cored to the depth ASTM F2170 specifies, sleeved and capped, and the probes read only after the method's waiting period, at the number of locations it calls for and at extra ones against the outside walls. A taped plastic sheet or a pinless meter screens for an obviously wet slab; neither gives the number a plank warranty is written against.
The plank and its carton
7 × 48 in (178 × 1219 mm) rigid-core plank, 10 to a carton, 23.33 sq ft (2.17 m²) a carton, no attached pad; the sheet modelled at a 3/8 in (10 mm) perimeter gap
Coverage read off the carton label, and the back of a plank checked for a bonded pad. The modelled label carries the nominal figure, 10 × 7 × 48 in multiplied out; a real label is taken as printed, because a plank sold as 7 × 48 in seldom measures exactly that on its face, and a printed 23.1 sq ft (2.15 m²) would still give 17 cartons. A pad already on the plank changes the underlayment line from rolls to none, and a second cushion under a click joint is a warranty problem rather than extra comfort.
The takeoff, in order
Each step needs something from the one before it, which is why the order is part of the answer.
Count the plank cartons and read the sheet inside them
- Needs
- The 348 sq ft (32.3 m²) from the floor measurements, the two fields added into one area because one plank and one waste band serve both, and the plan's five doorways, its outside corner and the break at the neck, which put it in the calculator's complex band rather than the plain-rectangle one.
- Produces
- 17 cartons, 396.7 sq ft (36.9 m²) of plank. As important is the sheet that comes with them: its flatness limit, moisture limit, perimeter gap and maximum run are the figures every later step is checked against, which is why the plank is settled before anything else.
Result17 cartons: 396.7 sq ft (36.9 m²) of plank for 348 sq ft (32.3 m²) of floor
LVP, Laminate & Engineered Floor CalculatorSize the levelling pour for the one low area
- Needs
- The flatness limit printed with the plank in step one, which the survey grid tests the slab against. Only the 8 × 10 ft (2.4 × 3.0 m) dish fails it, so the pour is sized on that dish's 80 sq ft (7.4 m²) and its 1/4 in (6.35 mm) average depth, not on the whole floor.
- Produces
- 12.5 gal (47.2 L) of compound — three to four bags before any allowance, across the yield range the calculator quotes for a 55 lb (25 kg) bag, the size that range is written for; many US levellers come in 50 lb bags, so the product's own data sheet makes the final conversion. The poured area is what step three primes, and the pour's dry-down sits in the schedule before any underlayment goes down.
Result12.5 gal (47.2 L) of levelling compound for the 80 sq ft (7.4 m²) dish
Self-Leveling Underlayment (SLU) Volume CalculatorDilute the primer for the pour area
- Needs
- The 80 sq ft (7.4 m²) pour area from step two — primer goes where compound goes, taken a little past the rim marked on the slab because the pour will run past it, but not across the whole floor — and a drop-of-water test that reads the slab as absorbent, which the modelled data sheet answers with a 1:1 mix covering 300 sq ft to the mixed gallon (7.36 m²/L), one coat.
- Produces
- About 17 fl oz (0.5 L) of neat primer and the same again of water, making 34 fl oz (1.01 L) of mix. It is bought as one 1 gal (3.79 L) jug, so the container rather than the coverage sets the order: the pour uses about an eighth of it, and carrying the coat past the rim changes nothing on the order.
Result0.13 gal (17 fl oz, 0.505 L) of neat primer, diluted 1:1 to 34 fl oz (1.01 L) of mix
Floor Primer Dilution and Coverage CalculatorCount the underlayment rolls
- Needs
- The same 348 sq ft (32.3 m²) as the cartons in step one, the fact that the plank chosen there has no pad on its back — the only reason a separate roll is right — and a slab already levelled in steps two and three, because an underlayment spans a hollow and leaves it there.
- Produces
- Four 100 sq ft (9.29 m²) rolls of underlayment with an integral vapour barrier, lapped and taped as its instructions say: the thin, dense roll the plank's sheet approves, not a soft laminate foam that lets a click joint flex. On a slab on grade the film, not the cushion, is the part doing the work; it is taken to the wall as the maker's instructions say, turned up behind the baseboard where they call for it, and never left as a soft filler in the gap step five holds.
Result4 rolls of 100 sq ft (9.29 m²): 400 sq ft (37.2 m²) under 348 sq ft (32.3 m²) of plank
Laminate/Vinyl Plank Floor Underlayment Roll CalculatorCount the spacers that hold the perimeter gap
- Needs
- The perimeter gap printed on the plank's sheet from step one, modelled at 3/8 in (10 mm), inside the roughly 5/16–1/2 in (8–12 mm) band the carton calculator's source gives, and the wall line the floor actually meets: the 94 ft (28.65 m) outline less the 13 ft 4 in (4.06 m) of doorways, where the floor stops at a transition strip instead of a wall. The spacing is 12 in (305 mm), the modelled reading of the plank's instructions.
- Produces
- 81 spacers along 80 ft 8 in (24.6 m) of wall. The count says nothing about the gap's width, which stays the plank maker's figure, and the same line of wall is the one step seven covers with baseboard once the spacers come out. The break at the neck needs the same gap on each side of its strip, but it is not wall and is not in this count.
Result81 spacers at 12 in (305 mm) centres along 80 ft 8 in (24.6 m) of wall
Floating Floor Perimeter Expansion Gap Spacer CalculatorMeasure the transition strips at the doorways and the neck
- Needs
- The five doorways left out of the wall line in step five — 36, 36, 30, 30 and 28 in (914, 914, 762, 762 and 711 mm) — plus the 48 in (1219 mm) neck, broken because the movement of both fields would otherwise be squeezed through that one strip of floor. Six openings of 208 in (5.28 m) in all average 34 2/3 in (881 mm), and each keeps the step-five gap inside its strip; the break also brings the longest field down to 20 ft (6.1 m), inside every run limit this site's calculators quote.
- Produces
- 18.2 ft (5.55 m) of transition strip at the calculator's small cutting allowance, bought as six pieces rather than one length: a T-molding across the neck with the gap held on both sides of it, an end cap against the front door's threshold, and at the kitchen tile, bedroom carpet and bathroom tile whichever strip bridges the height on the far side.
Result18.2 ft (5.55 m) of transition strip across five doorways and the neck
Floor Transition Strip CalculatorCount the baseboard in stock lengths
- Needs
- The wall line from step five, entered as the 32 × 15 ft (9.75 × 4.57 m) rectangle whose 94 ft (28.65 m) perimeter the L-shaped outline shares, where the calculator's flat 3 ft (0.9 m) per door stands in for the measured openings, so its run reads 79.2 ft (24.2 m) rather than step five's 80 ft 8 in (24.6 m); the five doorways from step six, where the base stops at the casing; and the 3/8 in (10 mm) gap step five held, which the base must be thick enough to cover.
- Produces
- 91.1 linear ft (27.8 m) at the top of the cutting band, bought as six 16 ft sticks (4.8 m lengths in metric). It is nailed to the wall and never through the plank, and it comes last because it covers the gap the spacers held and stops where the transition strips do.
Result91.1 linear ft (27.8 m) of baseboard: six 16 ft sticks (six 4.8 m lengths in metric)
Baseboard & Trim Calculator
The figures
| Step | Calculator | Figure |
|---|---|---|
| Count the plank cartons and read the sheet inside them | LVP, Laminate & Engineered Floor Calculator | 17 cartons: 396.7 sq ft (36.9 m²) of plank for 348 sq ft (32.3 m²) of floor |
| Size the levelling pour for the one low area | Self-Leveling Underlayment (SLU) Volume Calculator | 12.5 gal (47.2 L) of levelling compound for the 80 sq ft (7.4 m²) dish |
| Dilute the primer for the pour area | Floor Primer Dilution and Coverage Calculator | 0.13 gal (17 fl oz, 0.505 L) of neat primer, diluted 1:1 to 34 fl oz (1.01 L) of mix |
| Count the underlayment rolls | Laminate/Vinyl Plank Floor Underlayment Roll Calculator | 4 rolls of 100 sq ft (9.29 m²): 400 sq ft (37.2 m²) under 348 sq ft (32.3 m²) of plank |
| Count the spacers that hold the perimeter gap | Floating Floor Perimeter Expansion Gap Spacer Calculator | 81 spacers at 12 in (305 mm) centres along 80 ft 8 in (24.6 m) of wall |
| Measure the transition strips at the doorways and the neck | Floor Transition Strip Calculator | 18.2 ft (5.55 m) of transition strip across five doorways and the neck |
| Count the baseboard in stock lengths | Baseboard & Trim Calculator | 91.1 linear ft (27.8 m) of baseboard: six 16 ft sticks (six 4.8 m lengths in metric) |
The waste factors, and why these ends of the ranges
| Material | Applied | Why |
|---|---|---|
| Vinyl plank | The calculator's complex-room band, then whole cartons | The plan is two rectangles, but five doorways each need a notch or an undercut jamb, the room's end wall turns an outside corner into the hallway, and the break at the neck ends every row that reaches it; each of those breaks the offcut chain that holds a plain room to the 7% band. At 12% the 348 sq ft (32.3 m²) becomes 389.8 sq ft (36.2 m²), 16.7 cartons, so 17. The calculator's own note asks for a full carton kept spare for repairs, and at 17 that carton only exists if the cuts come in under the band. |
| Levelling compound | The upper end of the calculator's own allowance for an irregular slab, then whole bags | A dish is irregular by definition, and compound flows past the rim the grid drew. With the 15% the calculator's note gives at its upper end, 12.5 gal (47.2 L) becomes about 14.3 gal (54.3 L): four 55 lb (25 kg) bags at the top of the 3.2–4.2 gal (12–16 L) yield range and five at the bottom. The product's data sheet decides which, and a pour that comes up a bag short cannot be topped up once the first bags have begun to set. |
| Primer | One container, whatever the arithmetic says | The pour area takes 17 fl oz (0.5 L) of neat primer at a 1:1 mix, and the smallest jug on the modelled data sheet is a gallon (3.79 L). No allowance changes that; the rounding is already most of the jug. A second coat, if the slab drinks the first, still comes out of the same container. |
| Underlayment | Whole rolls, with the rounding carrying the laps and the wall trims | Four 100 sq ft (9.29 m²) rolls put 400 sq ft (37.2 m²) down for 348 sq ft (32.3 m²) of floor. The calculator divides area by coverage and allows nothing for the laps a film-backed product asks for or the strips trimmed off at the walls, so the 52 sq ft (4.8 m²) of rounding is what pays for both — and the 4 ft (1.2 m) hallway leaves an offcut from whatever roll width is bought that only fits another narrow run. |
| Transition strips | One piece per opening in the strip that opening needs, never one shared length | The calculator's 5% on 17 ft 4 in (5.28 m) of openings comes to 18.2 ft (5.55 m), about 10 in (264 mm) spare across the whole job. It cannot be pooled: an end cap, a reducer and a T-molding are different products, so each opening gets its own piece, and a miscut one is a new piece rather than a trim. |
| Baseboard | The top of the calculator's cutting band, in the longest stick offered | The L-shaped outline has five inside corners to cope, one outside corner to mitre where the room's end wall turns into the hallway, and ten ends stopping against casings — more cuts for its length than a plain room. At 15% the 79.2 ft (24.2 m) run becomes 91.1 ft (27.8 m), six 16 ft sticks (4.8 m lengths in metric), and the long stick keeps scarf joints on the 32 ft (9.75 m) wall to the fewest the doorways allow. |
Where this estimate is most likely to be wrong
Plank cartons
either wayBoth field lengths on this plan — 20 ft (6.1 m) in the room and 12 ft (3.7 m) in the hallway — are almost exact multiples of a 48 in (1219 mm) plank once the gaps come off. Carrying each row's cut-off piece to the head of the following row would line its end joints up with the row before, so the cut-offs have to skip a row instead, and whether that costs planks depends on how well the cutting is rotated.
Narrow it by: Setting out a few rows on paper with the real gap before ordering, and deciding in advance which row each offcut will start.
Levelling compound
usually underThe grid average treats the dish as a tidy basin with a known edge. Compound flows until it finds its own level, so it runs past the rim the readings drew, fills saw cuts and cracks the survey never saw, and soaks into the slab wherever the primer went on thin. Every one of those takes compound the average-depth figure does not hold.
Narrow it by: Reading the grid at closer spacing inside the dish, marking the rim on the slab, and having the bag above the calculated count on site before the first is mixed.
The break at the neck, which the carton count does not see
usually underStep one enters the room and hallway as one area in one waste band, as if the rows ran on through the opening. With the floor broken under a T-molding at the neck, every row that reached it ends at a gap and starts again on the far side, so the hallway is its own short field whose end cuts cannot feed the room's rows, and its last row along the 4 ft (1.2 m) width is ripped to whatever that width leaves.
Narrow it by: Running the carton calculator for the room and the hallway separately, and setting out the hallway's rows on paper, before the order is placed.
Slab moisture, which no calculator here sizes
usually underThe underlayment's film is there for the vapour a slab inside the plank's limit still gives off. A reading above that limit is a different problem: it needs drying time, drying equipment or a moisture-mitigation system, and none of those is on this list or in any calculator on this site. The probes also need time in the slab before they can be read, which sits in the schedule ahead of the pour.
Narrow it by: Testing to ASTM F2170 weeks ahead of the delivery date, and getting the plank maker's limit and its test method in writing before relying on either.
Baseboard
either wayThe calculator deducts a flat 3 ft (0.9 m) at each of the five doorways. Here the openings plus their casings come to about 15 ft 2 in (4.6 m), within half a foot of that deduction, so the run itself is close. What moves the figure is the cutting: coping five inside corners on a fussy profile consumes more, and square corners with a plain profile consume less.
Narrow it by: Measuring each wall between casings and checking the corners with a square before settling the stick length and the cutting band.
Tools this job needs
Frequently asked questions
- How much LVP do I need for a 15 × 20 room and a hallway?
- For this plan, 348 sq ft (32.3 m²): 300 sq ft (27.9 m²) in the 15 × 20 ft (4.6 × 6.1 m) room and 48 sq ft (4.5 m²) in the 4 × 12 ft (1.2 × 3.7 m) hallway. Five doorways and the neck break put it in the 12% waste band: 389.8 sq ft (36.2 m²), or 16.7 cartons of 23.33 sq ft (2.17 m²), so 17 cartons, 396.7 sq ft (36.9 m²). A full carton kept spare for repairs makes eighteen.
- Do I need underlayment under vinyl plank on a concrete slab?
- On a slab the moisture protection has to come from somewhere, and the plank in this example has no pad on its back, so it goes over a thin, dense underlayment with an integral vapour barrier: four 100 sq ft (9.29 m²) rolls for 348 sq ft (32.3 m²). A plank with a pad already bonded to it takes no second cushion; over concrete it takes a vapour film such as 6-mil (0.15 mm) polyethylene where its maker calls for one.
- Does a concrete slab need levelling before vinyl plank goes down?
- Only where it fails the plank maker's flatness limit, commonly on the order of 1/8 in under 6.5 ft (3 mm under 2 m). Here one 80 sq ft (7.4 m²) dish averaging 1/4 in (6.35 mm) fails it and takes 12.5 gal (47.2 L) of self-levelling compound, four to five 55 lb (25 kg) bags once the 15% an irregular dish takes is added, over 17 fl oz (0.5 L) of neat primer diluted 1:1. Moisture is tested to ASTM F2170 before either.