RoofCostRoofing Squares Calculator
One roofing square is 100 sq ft of roof. Enter your roof size and waste allowance and this calculator turns it into the numbers you actually order with: squares, shingle bundles, approximate shingle count and underlayment rolls.
Use the ground footprint plus pitch in the other mode if this is a flat measurement.
Length × width is treated as the footprint and multiplied by the pitch factor to get true sloped area.
Only needed if you want a ridge-cap bundle count.
Materials to order
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| Shingle bundles (3 per square) | — |
| Approx. individual shingles | — |
| Synthetic underlayment rolls (10 sq / roll) | — |
| Ridge-cap bundles (≈33 lin ft / bundle) | — |
Counts are rounded up to whole purchasable units and include your waste allowance. Bundle coverage varies by brand — architectural shingles are still packed 3 bundles per square by most manufacturers, but check the wrapper before ordering. One synthetic underlayment roll nominally covers 1,000 sq ft (10 squares); a #15 felt roll covers about 400 sq ft (4 squares).
How roofers count materials
Squares first. Everything in roofing is priced and ordered by the square — 100 sq ft of sloped roof surface. A 2,340 sq ft roof is 23.4 squares on paper, but nobody orders 23.4 squares of anything: you add waste for cuts, starters and ridge, then round up to whole bundles.
Bundles and shingles. Most shingles are packed so 3 bundles cover one square. A bundle of 3-tab shingles holds roughly 29 individual shingles; architectural bundles hold fewer, larger shingles but cover the same area. That is why this calculator counts bundles as the ordering unit and treats the shingle count as an approximation.
Underlayment is separate. Synthetic underlayment comes in 10-square rolls, felt in 4-square (#15) or 2-square (#30) rolls. Ice-and-water shield for eaves, valleys and penetrations is figured by the roll on top of that, based on local code — in cold climates typically the first 3–6 ft from the eave.
Ordering for a job? Pair this with the roof replacement cost calculator to sanity-check a material quote, or the metal roof cost calculator if you are pricing panels instead of shingles.
Frequently asked questions
How many bundles are in a roofing square?
Three bundles per square for most shingles sold today — one bundle covers about 33.3 sq ft, and three make up the 100 sq ft of a square. That applies to standard 3-tab and most architectural shingles, though heavier premium lines can run 4–5 bundles per square. Always confirm on the wrapper: coverage per bundle is printed on every pack.
How do I calculate roofing squares?
Divide the total sloped roof area in square feet by 100. If you only know the footprint, multiply it by the pitch factor first — 1.118 for a 6/12 roof, 1.202 for 8/12, 1.414 for 12/12. Then add a waste allowance (10% is typical for a gable roof, 15% for a hip roof) before converting to bundles.
How much waste should I add?
About 10% for a simple gable roof, 12–15% for hip roofs and roofs with valleys, and up to 20% for complex cut-up roofs. The waste factor covers starter courses, ridge caps, cuts at hips and valleys, and the inevitable damaged shingles.
How many rolls of underlayment do I need?
A standard synthetic underlayment roll covers about 1,000 sq ft (10 squares), so divide your roof area including waste by 1,000 and round up. Traditional #15 felt covers roughly 400 sq ft (4 squares) per roll, and #30 felt about 200 sq ft (2 squares). Ice-and-water shield is ordered separately by the roll for eaves and valleys.