Roofing Calculator
Estimate a full roofing job from your house footprint and pitch: squares of roof surface, shingle bundles, underlayment rolls, nails and total material cost — the numbers a supplier will ask for.
Include eave overhangs
Unknown? Use the roof pitch calculator
Architectural shingles: $130–$180/square materials
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You might also need:Roof Pitch Calculator·Shingle Calculator
How roof area is estimated
squares = surface ÷ 100 · bundles = squares × 3
A 40 × 30 ft footprint under a 6/12 roof has 1,342 sq ft of actual surface — call it 14.8 squares with 10% waste, or 45 bundles of shingles. The pitch multiplier is what ground-level measurements miss: steeper roofs have dramatically more surface than their footprint.
Material checklist per square
| Material | Per square |
|---|---|
| Shingle bundles | 3 |
| Roofing nails (1¼″) | ~320 nails / 2¼ lb |
| Synthetic underlayment | 1/10 roll (10-square rolls) |
| Starter strip | ~⅓ bundle along eaves |
| Ridge caps | ~1 bundle per 33 lin ft of ridge/hip |
Before you order
- Verify the pitch: a wrong multiplier compounds across the whole job — measure it properly with the roof pitch calculator.
- Bundle-level detail (starter, ridge, staggered exposure) lives in the shingle calculator.
- Structural work too? New rafters are covered by the rafter calculator.
- Tear-off adds disposal: old shingles weigh 250–350 lb per square — a 20-square tear-off fills most of a 10-yard dumpster.
Frequently asked questions
What is a square in roofing?+
One roofing square is 100 square feet of roof surface. Roofers quote everything in squares: a "20-square roof" has 2,000 sq ft of surface. Shingles come three bundles to the square.
How much does a new roof cost?+
Architectural asphalt shingles installed run $450–$700 per square in most US markets, so a typical 20-square roof lands between $9,000 and $14,000 including tear-off. Materials alone are $130–$180 per square — the rest is labor, disposal and accessories.
How do I measure my roof from the ground?+
Measure the house footprint (length × width including eave overhangs), then multiply by the pitch multiplier — 1.054 for a 4/12 roof, 1.118 for 6/12, 1.202 for 8/12. This calculator does the multiplication for you and adds waste.
How much waste should I add on shingles?+
Add 10% for simple gable roofs and 15% for hips, valleys and dormers — cut shingles at every hip and valley become scrap. Complex roofs with multiple facets can hit 20%.
What else do I need besides shingles?+
Underlayment (synthetic felt covers ~10 squares per roll), ice-and-water shield for eaves and valleys in cold climates, starter strip, ridge caps, drip edge, and about 320 nails per square (2¼ lb). This calculator counts underlayment and nails for you.