Why does the plan area under-order blanket?

Because a slope face is the hypotenuse of the triangle a plan view shows only the base of. On a 3:1 batter the face is 5.4% longer than the plan distance, and on a 1:1 batter it is 41.4% longer. Order from the plan area on a steep face and you are a strip and a half short by the time the crew reaches the end.

Does the shingle lap direction really matter?

It decides whether the blanket stays on. The upslope roll must lap over the roll below it so runoff crosses the joint on the surface. Lapped the other way, water runs straight into the seam, lifts the lower roll's edge and unzips the strip from the middle of the face outward.

Can I reduce the staple count on a gentle slope?

Only to whatever your product's own pattern chart allows for that slope. The staple density is part of what was tested under ASTM D6459 — the rating describes a blanket held down a particular way, and a blanket at half density is a different installation with no test behind it.

The face drains into a ditch — can I size the ditch lining here as well?

No. A channel carries concentrated flow, so the product there is selected against the shear stress it has to survive rather than against slope steepness — that is what ASTM D6460 measures in an earthen channel, and it is a different test from ASTM D6459, the rainfall-on-a-hillslope method a slope rating comes from. This page counts rolls and staples over a slope face; it selects a product against neither test. The take-off differs as well: a channel is lined across its whole wetted perimeter, bottom and both side slopes, rather than as strips down one rectangular face, and the details usually add check slots cut across the channel at intervals. Neither is counted here. Take the face off this page and let the ditch be its own line.

Does the anchor trench allowance cover the toe as well as the crest?

Only if you put it there. The field adds one length to every strip, so everything your detail buries — crest trench, toe trench, any mid-slope check slot — has to be totalled into that single figure before it is entered. The default of 0.9 m (about 3 ft) stands for a crest trench on its own. Watch what the change does to the roll count as well: on a face already sitting close to a roll boundary, adding a toe anchor can push every strip onto a second roll. The digging and backfilling of the trench is not in here at all — this is blanket length only.

There is a bench across the middle of my slope. Do I run it as one face?

No. The page models the slope as one rectangle at one ratio, so a benched profile is three take-offs: the upper batter with its own plan distance and ratio, the lower batter with its own, and the bench itself. The bench has no batter, and the ratio field will not accept flat, so run it at the flattest setting the field allows — 20 — which stretches that strip by about one part in eight hundred and nothing more. Add the three answers. Give each grade break its own anchoring while you are at it — blanket carried straight through a break commonly bridges it, and water that gets beneath a bridged section rills away out of sight. Nothing is deducted for inlets, headwalls or steps either; the count covers the full rectangle, and the offcut around a round structure is scrap regardless.

Heavy Civil & Infrastructure

Erosion Control Blanket Roll and Staple Calculator

Rolls and staples for a slope face, counted against the true face area rather than the plan area a drawing shows.

Answers as you typeNo submit button
Every formula citedNamed published standards
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Market

Imperial · sales tax

Horizontal Distance from Toe to Crest

The distance up the slope as it appears on plan, measured horizontally.

This is the number you scale off a drawing. It is not the distance a roll has to travel down the face — that is longer, and this page works out by how much from the slope ratio below.

Slope Ratio (horizontal run per unit of rise)

Enter 3 for a 3:1 batter — three across for every one up.

Flatter slopes have a larger number here. A 3:1 face is only 5% longer than its plan distance, but a 1:1 face is 41% longer, and that difference is entirely material you either ordered or did not.

Width of Face to Cover

The distance along the slope, measured across the direction the rolls run.

Rolls run down the face, so this dimension decides how many parallel strips are needed. Measure it along the crest rather than along the toe if the two differ.

Roll Width

The width of the product as supplied, from its data sheet.

Common widths are 8 ft (2.44 m) and 16 ft (4.88 m) for hillslope blanket. The wider product needs fewer seams, which matters more on a long face than the price difference usually suggests.

Roll Length

The length on the roll as supplied, from the same data sheet.

Hillslope blanket is commonly put up in 112.5 ft (34.3 m) or 110 ft (33.5 m) rolls; channel product runs shorter and heavier. Confirm against the roll you are actually buying rather than the family it belongs to.

Side Overlap Between Adjacent Strips

How far each strip laps over the one beside it.

The installation detail on the product's own sheet governs, and 4 in (100 mm) is a common figure. The lap is lost coverage: it is why the strip count is worked out on an effective width rather than the roll width.

End Overlap Where One Roll Meets the Next

The shingle lap where an upslope roll runs over the roll below it.

The upper roll always laps OVER the lower one, so water runs across the joint rather than into it. A reversed shingle lap is the commonest reason a blanket peels from the middle of a face.

Anchor Trench Allowance per Strip

The extra material each strip needs to turn down into the crest trench and be backfilled.

A typical detail buries the blanket in a trench at the top of slope and folds it back over the backfill, which consumes roughly a metre of material per strip. Take the figure from your detail; enter zero if the crest is anchored some other way.

Staple Pattern (from the product's chart)

The staple density the manufacturer's slope chart calls for at your slope and product.

Every manufacturer prints a pattern chart keyed to slope steepness and, for channel work, to shear stress. The pattern is a tested part of the product's performance, not a site decision — a blanket stapled at half its rated density is not the product that was tested.

Blanket rolls needed

17 rolls

Medium confidence

Roll and strip counts round up whole units, so a face whose width is a fraction over a strip boundary buys a full extra roll. Seeding, tackifier and the trench excavation are separate items.

Slope face length: 62.19 ft
Slope face area: 8,084.89 ft²
Plan area of the same slope: 7,670 ft²
Strips across the face: 17 strips
Rolls per strip: 1 roll
Staples required: 1,797 staples
Material purchased: 14,960 ft²

Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

ASTM D6459 Standard Test Method for Determination of Rolled Erosion Control Product Performance in Protecting Hillslopes from Rainfall-Induced Erosion — the hillslope test a product's slope rating comes from
ASTM D6460 Standard Test Method for Determination of Rolled Erosion Control Product Performance in Protecting Earthen Channels from Stormwater-Induced Erosion — the channel counterpart, which governs blanket in a ditch rather than on a face
Staple density is taken from the product's own staple pattern chart, which is why it is selected rather than derived. The densities offered are the per-square-yard patterns those charts are printed in
Face area = plan distance x sqrt(1 + (1/n)²) for a slope of n horizontal to 1 vertical — plain geometry, not a published coefficient, and the reason a plan take-off under-orders blanket

Inputs used

Horizontal Distance from Toe to Crest: 59 ft
Slope Ratio (horizontal run per unit of rise): 3
Width of Face to Cover: 130 ft
Roll Width: 8 ft
Roll Length: 110 ft
Side Overlap Between Adjacent Strips: 4 in
End Overlap Where One Roll Meets the Next: 11.75 in
Anchor Trench Allowance per Strip: 3 ft
Staple Pattern (from the product's chart): 2 per sq yd (2.39 per m²)

Intermediate steps

Slope face length: 62.19 ft
Slope face area: 8,084.89 ft²
Plan area of the same slope: 7,670 ft²
Strips across the face: 17 strips
Rolls per strip: 1 roll
Staples required: 1,797 staples
Material purchased: 14,960 ft²

Final result17 rolls

Confidence note: Roll and strip counts round up whole units, so a face whose width is a fraction over a strip boundary buys a full extra roll. Seeding, tackifier and the trench excavation are separate items.

What this calculation does not cover

Hillslope geometry only. Blanket in a channel is governed by shear stress under ASTM D6460 and is not sized here.
The staple pattern is taken from your product chart; this page counts staples, it does not select the pattern.
No allowance for cutting around structures, inlets or benches — deduct or add those separately.

Estimated cost — your price

Price per roll ($)

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.

Schematic, drawn to the proportions you entered — not to scale on screen.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-03 · in the site-wide review of 2026-09-06 · v1.0.1

Regulatory standards & verification citations4

ASTM D6459 Standard Test Method for Determination of Rolled Erosion Control Product Performance in Protecting Hillslopes from Rainfall-Induced Erosion — the hillslope test a product's slope rating comes from
ASTM D6460 Standard Test Method for Determination of Rolled Erosion Control Product Performance in Protecting Earthen Channels from Stormwater-Induced Erosion — the channel counterpart, which governs blanket in a ditch rather than on a face
Staple density is taken from the product's own staple pattern chart, which is why it is selected rather than derived. The densities offered are the per-square-yard patterns those charts are printed in
Face area = plan distance x sqrt(1 + (1/n)²) for a slope of n horizontal to 1 vertical — plain geometry, not a published coefficient, and the reason a plan take-off under-orders blanket

Which documents these citations point at

Standards referenced: ASTM D6459, ASTM D6460 (ASTM International, United States).

Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

Sizing a Swale or Roadside Ditchuses this calculator
Peak flow is handed to you by the catchment and the storm. The channel is the only part you get to design, and it has to pass two checks, not one.

Called something else where you work? Sustainable drainage — the term in each market, how close the equivalence really is, and the standard that governs it.

Still deciding? Riprap vs Erosion Control Blanket — the factors that actually differ, with no invented prices.

How to calculate erosion control blanket roll and staple in 10 steps

Horizontal Distance from Toe to CrestThe distance up the slope as it appears on plan, measured horizontally.
Slope Ratio (horizontal run per unit of rise)Enter 3 for a 3:1 batter — three across for every one up.
Width of Face to CoverThe distance along the slope, measured across the direction the rolls run.
Roll WidthThe width of the product as supplied, from its data sheet.
Roll LengthThe length on the roll as supplied, from the same data sheet.
Side Overlap Between Adjacent StripsHow far each strip laps over the one beside it.
End Overlap Where One Roll Meets the NextThe shingle lap where an upslope roll runs over the roll below it.
Anchor Trench Allowance per StripThe extra material each strip needs to turn down into the crest trench and be backfilled.
Staple Pattern (from the product's chart)The staple density the manufacturer's slope chart calls for at your slope and product.
Blanket rolls neededThe tool computes the blanket rolls needed from those figures and shows the formula, its sources, and a confidence rating alongside it.

Frequently asked questions

Why does the plan area under-order blanket?: Because a slope face is the hypotenuse of the triangle a plan view shows only the base of. On a 3:1 batter the face is 5.4% longer than the plan distance, and on a 1:1 batter it is 41.4% longer. Order from the plan area on a steep face and you are a strip and a half short by the time the crew reaches the end.
Does the shingle lap direction really matter?: It decides whether the blanket stays on. The upslope roll must lap over the roll below it so runoff crosses the joint on the surface. Lapped the other way, water runs straight into the seam, lifts the lower roll's edge and unzips the strip from the middle of the face outward.
Can I reduce the staple count on a gentle slope?: Only to whatever your product's own pattern chart allows for that slope. The staple density is part of what was tested under ASTM D6459 — the rating describes a blanket held down a particular way, and a blanket at half density is a different installation with no test behind it.
The face drains into a ditch — can I size the ditch lining here as well?: No. A channel carries concentrated flow, so the product there is selected against the shear stress it has to survive rather than against slope steepness — that is what ASTM D6460 measures in an earthen channel, and it is a different test from ASTM D6459, the rainfall-on-a-hillslope method a slope rating comes from. This page counts rolls and staples over a slope face; it selects a product against neither test. The take-off differs as well: a channel is lined across its whole wetted perimeter, bottom and both side slopes, rather than as strips down one rectangular face, and the details usually add check slots cut across the channel at intervals. Neither is counted here. Take the face off this page and let the ditch be its own line.
Does the anchor trench allowance cover the toe as well as the crest?: Only if you put it there. The field adds one length to every strip, so everything your detail buries — crest trench, toe trench, any mid-slope check slot — has to be totalled into that single figure before it is entered. The default of 0.9 m (about 3 ft) stands for a crest trench on its own. Watch what the change does to the roll count as well: on a face already sitting close to a roll boundary, adding a toe anchor can push every strip onto a second roll. The digging and backfilling of the trench is not in here at all — this is blanket length only.
There is a bench across the middle of my slope. Do I run it as one face?: No. The page models the slope as one rectangle at one ratio, so a benched profile is three take-offs: the upper batter with its own plan distance and ratio, the lower batter with its own, and the bench itself. The bench has no batter, and the ratio field will not accept flat, so run it at the flattest setting the field allows — 20 — which stretches that strip by about one part in eight hundred and nothing more. Add the three answers. Give each grade break its own anchoring while you are at it — blanket carried straight through a break commonly bridges it, and water that gets beneath a bridged section rills away out of sight. Nothing is deducted for inlets, headwalls or steps either; the count covers the full rectangle, and the offcut around a round structure is scrap regardless.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.