Roofing Material Calculator
Calculate how much roofing material you need — enter your roof footprint and pitch to get roofing squares, shingle bundles, underlayment, drip edge and nails, with a shopping list.
How to calculate roofing materials
Roofing is ordered by the square — 100 square feet of roof surface. To find how many you need, start with your building footprint (length × width), multiply by the slope factor for your pitch to get the true sloped area, add a waste allowance, then divide by 100. The calculator above does all of this and converts the result into the exact quantities you buy.
roof area = footprint × slope factor · squares = (roof area × (1 + waste%)) ÷ 100 · bundles = squares × 3
Most shingles come 3 bundles to a square. On top of shingles you need underlayment (synthetic rolls cover about 10 squares each), drip edge along the eaves and rakes, and roughly 2.5 lbs of roofing nails per square. A simple gable roof needs about 10% waste; a cut-up roof with hips, valleys and dormers can need 15% or more.
What you'll need per roof size
| Roof area | Squares | Shingle bundles | Underlayment rolls |
|---|---|---|---|
| 1,500 sq ft | 15 | 45 | 2 |
| 2,000 sq ft | 20 | 60 | 2 |
| 2,500 sq ft | 25 | 75 | 3 |
| 3,000 sq ft | 30 | 90 | 3 |
Quantities above are for the sloped area shown, before waste — add 10–15% for cuts, starter and ridge.
Not sure of your pitch? Use the roof pitch calculator to get your slope factor first. Ready to price it out? The roof replacement cost calculator turns your roof size into an installed cost estimate by material.
Frequently asked questions
How many bundles of shingles do I need?
Most architectural and 3-tab shingles come 3 bundles to a square, where a square covers 100 sq ft of roof. So you need about 3 bundles for every 100 sq ft of actual sloped roof area, plus extra for waste, ridges and starter rows. This calculator works out the squares from your footprint and pitch, then converts to bundles including a waste allowance.
What is a roofing square?
A roofing square is 100 square feet of roof surface — the standard unit roofers and suppliers use to quote material and labor. A 2,000 sq ft roof is 20 squares. Shingles, underlayment and labor pricing are all quoted per square, which is why the calculator converts your area into squares first.
How do I measure my roof area from the ground?
Measure the length and width of the building footprint the roof covers, multiply for the footprint area, then multiply by the slope factor for your pitch to get the true sloped area. For a complex roof, add up each rectangular section. Use the roof pitch calculator to get the slope factor, or pick your pitch from the dropdown here and the tool applies it.
How much extra should I add for waste?
A simple gable roof typically needs about 10% extra for cuts, starter and ridge; a complex roof with lots of hips, valleys and dormers can need 15% or more. This calculator defaults to 10% and lets you raise it — ordering a little extra is cheaper than a second delivery mid-job.
How many nails do I need per square of shingles?
At the standard 4 nails per shingle, a square of three-tab shingles uses roughly 320 nails, or about 480 in high-wind areas at 6 nails per shingle. As a rule of thumb that is about 2.5 lbs of roofing nails per square. The calculator estimates total nail weight from your squares.