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Roofing underlayment chart
Put your roof area and roll coverage in: 2,000 square feet at 10% waste needs 5.50 rolls, order 6 rolls.
★ CONSTRUCTION · ROOFING · UNDERLAYMENT
Roofing Underlayment Chart: 6 Rolls for 2,000 Sq Ft
On the defaults — a 2,000-square-foot roof, rolls covering 400 square feet each, and 10% waste — you need 5.50 rolls of underlayment exact, so order 6 rolls. This is the UNDERLAYMENT version — rolls under the shingles — the roofing-shingle-chart page is the SHINGLE version — bundles by roof size and waste; the topsoil-coverage-chart page is the TOPSOIL version — cubic yards and tons by area and depth; and the gravel-depth-chart page is the GRAVEL version — yards and tons by area and depth.
What does 5.50 rolls mean?
It means a 2,000-square-foot roof needs five and a half rolls of underlayment once 10% waste is added: 2,000 × 1.10 ÷ 400 is 5.50, and since suppliers sell whole rolls, the order is 6 rolls. The 1.10 is the whole story in miniature — overlaps, cuts around valleys and ridges, and trimming at the edges all eat material, so the bare roof area alone understates the order: without waste the same roof needs exactly 5.00 rolls, and the waste half-roll is what keeps the last strip of roof covered. The part people get wrong is ordering the exact figure: 5.50 rolls cannot be bought, and ordering 5 leaves half a roll of roof bare.
Three things to check before you trust the number
Is the area really 2,000 square feet? Roofs are sloped, so the roof surface is larger than the floor below it: a 2,000-square-foot footprint under a steep pitch can be a 2,500-square-foot roof, and the roll count follows it exactly — the 3,000-square-foot branch needs 8.25 rolls exact, order 9, while the 1,000-square-foot branch needs 2.75, order 3. Measure each slope separately and add the areas.
Is the roll coverage really 400 square feet? Roll labels often quote the raw roll size, but overlaps steal 2–4 inches per course, so the covered figure is smaller: the 200-square-foot-coverage branch needs 11.00 rolls exact, order 11, while the 1,000-square-foot-coverage branch needs 2.20, order 3, for the same 2,000-square-foot roof. Use the coverage after overlaps from the label, or measure one laid course yourself.
Have you ordered the rounded-up figure? This chart gives the exact rolls and the order quantity separately for a reason: suppliers sell whole rolls, and a partial roll is still a roll you must buy. The headline exact figure is 5.50 rolls but the order is 6 rolls, and the 3,000-square-foot branch is 8.25 rolls exact but 9 rolls to order — ordering the exact figure leaves the last strip of the roof bare.
Worked example
On the defaults: 2,000 square feet, rolls covering 400 square feet, 10% waste.
- Area with waste: 2,000 × 1.10 is 2,200 square feet.
- Exact rolls: 2,200 ÷ 400 is 5.50 rolls.
- Order: 5.50 rounded up is 6 rolls.
And the other way: the roof area needing exactly 5.50 rolls at 400 square feet a roll is 2,000 square feet, the roll coverage needing exactly 5.50 rolls over 2,000 square feet is 400 square feet, and the roof area needing exactly 11.00 rolls at 400 square feet a roll is 4,000 square feet.
Underlayment rolls lookup: roof area × roll coverage (10% waste included)
| Roof area | Roll coverage | Exact rolls | Order |
|---|---|---|---|
| 500 sq ft | 200 sq ft | 2.75 rolls | 3 rolls |
| 500 sq ft | 400 sq ft | 1.38 rolls | 2 rolls |
| 500 sq ft | 500 sq ft | 1.10 rolls | 2 rolls |
| 500 sq ft | 1,000 sq ft | 0.55 rolls | 1 rolls |
| 1,000 sq ft | 200 sq ft | 5.50 rolls | 6 rolls |
| 1,000 sq ft | 400 sq ft | 2.75 rolls | 3 rolls |
| 1,000 sq ft | 500 sq ft | 2.20 rolls | 3 rolls |
| 1,000 sq ft | 1,000 sq ft | 1.10 rolls | 2 rolls |
| 2,000 sq ft | 200 sq ft | 11.00 rolls | 11 rolls |
| 2,000 sq ft | 400 sq ft | 5.50 rolls | 6 rolls |
| 2,000 sq ft | 500 sq ft | 4.40 rolls | 5 rolls |
| 2,000 sq ft | 1,000 sq ft | 2.20 rolls | 3 rolls |
| 3,000 sq ft | 200 sq ft | 16.50 rolls | 17 rolls |
| 3,000 sq ft | 400 sq ft | 8.25 rolls | 9 rolls |
| 3,000 sq ft | 500 sq ft | 6.60 rolls | 7 rolls |
| 3,000 sq ft | 1,000 sq ft | 3.30 rolls | 4 rolls |
Exact rolls are roof area × 1.10 ÷ roll coverage; order rounds up to whole rolls, so a 5.50-roll figure orders 6 rolls.
Every branch, checked
- 1,000 sq ft roof, 400 sq ft rolls: 1,000 sq ft roof, 400 sq ft rolls: 2.75 rolls exact — order 3 rolls.
- 3,000 sq ft roof, 400 sq ft rolls: 3,000 sq ft roof, 400 sq ft rolls: 8.25 rolls exact — order 9 rolls.
- 2,000 sq ft roof, 200 sq ft rolls: 2,000 sq ft roof, 200 sq ft rolls: 11.00 rolls exact — order 11 rolls.
- 2,000 sq ft roof, 1,000 sq ft rolls: 2,000 sq ft roof, 1,000 sq ft rolls: 2.20 rolls exact — order 3 rolls.
- 500 sq ft roof, 400 sq ft rolls: 500 sq ft roof, 400 sq ft rolls: 1.38 rolls exact — order 2 rolls.
- 2,000 sq ft roof, 500 sq ft rolls: 2,000 sq ft roof, 500 sq ft rolls: 4.40 rolls exact — order 5 rolls.
The reverses, worked backwards
- Roof area needing exactly 5.50 rolls at 400 sq ft a roll: 2,000 sq ft — at 2,000 sq ft the figures are 5.50 rolls exact — order 6 rolls.; at the lower neighbor the figures are 5.23 rolls exact — order 6 rolls.; at the upper neighbor the figures are 5.78 rolls exact — order 6 rolls..
- Roll coverage needing exactly 5.50 rolls over 2,000 sq ft: 400 sq ft — at 400 sq ft the figures are 5.50 rolls exact — order 6 rolls.; at the lower neighbor the figures are 6.29 rolls exact — order 7 rolls.; at the upper neighbor the figures are 4.89 rolls exact — order 5 rolls..
- Roof area needing exactly 11.00 rolls at 400 sq ft a roll: 4,000 sq ft — at 4,000 sq ft the figures are 11.00 rolls exact — order 11 rolls.; at the lower neighbor the figures are 10.73 rolls exact — order 11 rolls.; at the upper neighbor the figures are 11.28 rolls exact — order 12 rolls..
What the defaults assume
The defaults are a 2,000-square-foot roof and 400-square-foot rolls, so the headline is a medium house roof at a common roll size. The model is one multiplication, one division and a round-up: area times 1.10 for waste, divided by roll coverage, then rounded up to whole rolls — with a tiny epsilon subtracted before the ceiling so a value landing exactly on a whole roll, like 2,000 square feet at 440-square-foot coverage, orders that roll and not one more. The area reverses are checked at 100 square feet either side; the coverage reverse is checked at 50 square feet either side. The model does not include valleys, ridges, hips, starter courses or delivery minimums — complex roofs want an extra 5% beyond the 10% waste here, and most suppliers have a minimum order.
Output · formula · meaning
| Output | Formula | What it means |
|---|---|---|
| Exact rolls | roof area × 1.10 ÷ roll coverage | 5.50 rolls — 2,000 × 1.10 ÷ 400. |
| Order rolls | exact rolls rounded up to whole rolls | 6 rolls — 5.50 rounded up. |
| Roof area behind a target roll count | target rolls × roll coverage ÷ 1.10 | 2,000 sq ft — 5.50 × 400 ÷ 1.10. |
| Roll coverage behind a target roll count | roof area × 1.10 ÷ target rolls | 400 sq ft — 2,000 × 1.10 ÷ 5.50. |
| 1,000 sq ft roof, 400 sq ft rolls | same model | 2.75 rolls exact — order 3 rolls. |
| 3,000 sq ft roof, 400 sq ft rolls | same model | 8.25 rolls exact — order 9 rolls. |
| 2,000 sq ft roof, 200 sq ft rolls | same model | 11.00 rolls exact — order 11 rolls. |
| 2,000 sq ft roof, 1,000 sq ft rolls | same model | 2.20 rolls exact — order 3 rolls. |
| 500 sq ft roof, 400 sq ft rolls | same model | 1.38 rolls exact — order 2 rolls. |
| 2,000 sq ft roof, 500 sq ft rolls | same model | 4.40 rolls exact — order 5 rolls. |
| Roof area needing exactly 5.50 rolls at 400 sq ft a roll | reverse | 2,000 sq ft: 5.50 rolls exact — order 6 rolls. |
| Roll coverage needing exactly 5.50 rolls over 2,000 sq ft | reverse | 400 sq ft: 5.50 rolls exact — order 6 rolls. |
| Roof area needing exactly 11.00 rolls at 400 sq ft a roll | reverse | 4,000 sq ft: 11.00 rolls exact — order 11 rolls. |
| 0 sq ft roof | same model | 0.00 rolls exact — order 0 rolls. |
| Negative roof area | same model | Roof area — 0 or more. |
| Negative roll coverage | same model | Roll coverage — more than 0. |
| 2,000 sq ft, 440 sq ft rolls — exactly 5.00 rolls | same model | 5.00 rolls exact — order 5 rolls. |
Who uses this
- A roofer ordering underlayment — 2,000 square feet at 400 square feet a roll is 5.50 rolls exact, order 6.
- A homeowner checking a roofer quote — the lookup table gives exact and order rolls for four roof areas and four roll sizes.
- Someone choosing a roll size — the 200-square-foot branch needs 11 rolls and the 1,000-square-foot branch needs 3 for the same roof.
- A buyer checking a supplier quote — the reverses give the roof area or roll coverage behind any quoted roll count.
Accuracy & limitations
Figures are the model’s own arithmetic on the numbers you type, computed from unrounded values and displayed rounded HALF_UP to 2dp, with order rolls rounded up to whole rolls. The main limitation is the roof itself, not the arithmetic: pitch, valleys, hips and ridges all move the real order, and the 10% waste figure is a standard allowance, not a measurement of your roof. This page is a calculation tool, not a roofing quote.
Cite this calculator
2,000 sq ft at 10% waste needs 5.50 rolls of underlayment at 400 sq ft a roll — order 6 rolls. Source: Bright Side Kit, https://brightoolbox.com/roofing-underlayment-chart/, accessed 28 October 2026.
Frequently asked questions
How many rolls of underlayment do I need?
Divide the roof area with waste by the roll coverage, then round up: 2,000 square feet times 1.10 divided by 400 square feet is 5.50 rolls exact, so order 6 rolls.
Why add 10% waste?
Overlaps, cuts around valleys and ridges, and trimming at edges all consume material. Without waste the same roof needs exactly 5.00 rolls; the extra half-roll is what keeps the last strip covered.
Should I use the flat floor area or the sloped roof area?
The sloped roof area. A pitched roof is larger than the footprint beneath it, so the floor area understates the order — measure each slope separately and add them.
What roll coverage should I type in?
The coverage after overlaps, from the roll label — not the raw roll size. Overlaps steal 2–4 inches per course, so the covered figure is smaller than the roll itself.
Why does the order round up instead of rounding to nearest?
Suppliers sell whole rolls, and a partial roll cannot cover a partial roof. Rounding 5.50 down to 5 would leave half a roll of roof bare; rounding up to 6 covers it with a little spare.
What if my roof has valleys and hips?
Add extra waste beyond the 10% here — complex roofs commonly want 15% in total. Work out the order at 10%, then add one extra roll for a complex roof as a safety margin.