Roofing Calculator — How Many Shingles Do I Need?

Enter your roof footprint and pitch to get shingle bundles, roofing squares, and underlayment rolls needed.

How to Calculate Roofing Materials

Start with your roof's footprint (the house dimensions from above, not the actual sloped surface). Multiply length × width to get the footprint area, then multiply by a pitch factor to get the true roof surface area — a steeper roof has more actual surface than its footprint suggests.

Divide the roof area by 100 to get roofing squares (the standard unit roofers use), then multiply by bundles-per-square for your shingle type. Always add a waste factor for cuts at ridges, valleys, and edges.

Roof Pitch Multipliers

A 2,000 sq ft footprint at a 6:12 pitch has roughly 2,236 sq ft of actual roof surface — that's the number your shingle order needs to be based on, not the footprint.

Common Roofing Estimate Mistakes

• Using footprint square footage instead of actual roof area. A 2,000 sq ft house footprint isn't a 2,000 sq ft roof — the pitch multiplier adds anywhere from 3% (low-slope) to over 40% (steep roofs) of extra surface that has to be shingled.
• Forgetting ridge cap and starter strip shingles. These are sold separately from field shingles and are easy to leave off a materials list, but every roof needs them along ridges, hips, and eaves.
• Not accounting for waste on cut-heavy roofs. A simple gable roof wastes very little material. A roof with multiple valleys, dormers, or hips can waste 15% or more — order a flat 10% extra only for simple roof shapes.
• Mixing shingle bundles from different production runs. Like paint and flooring, shingle color can vary subtly batch to batch. Order all bundles for one roof in a single purchase when possible.
• Skipping underlayment and drip edge in the budget. Shingles are only part of a roofing system — synthetic underlayment, ice-and-water shield in cold climates, and drip edge flashing all add real cost that's easy to forget when only pricing shingles.

Frequently Asked Questions

How many bundles of shingles do I need per square?

Most standard 3-tab and architectural asphalt shingles come 3 bundles per square (100 sq ft). Heavier wood shake typically needs 4 bundles per square.

How does roof pitch affect the amount of shingles I need?

A steeper pitch means more actual roof surface area than the home's footprint suggests. A 6:12 pitch adds about 12% more area than the flat footprint; a 12:12 pitch adds about 41%.

What is a roofing square?

A roofing square equals 100 square feet of roof surface. It's the standard unit roofers and suppliers use to price and order materials.

How much waste should I add for a roofing job?

Add 10% for a simple gable roof, and 15% for roofs with hips, valleys, or dormers, since those features create more angled cuts and offcuts.