Roofing Calculator
Calculate roofing squares, shingles, underlayment, and materials needed for your roof. Includes pitch factor, waste allowance, and cost estimates.
How to Use This Calculator
Accurately estimating roofing materials prevents costly mid-project supply runs and excess material waste. Here's how to get it right:
- Choose your input method: enter total roof square footage directly, or enter length and width dimensions.
- Select your roof pitch. If you don't know it, measure the rise (vertical height) for every 12 inches of horizontal run.
- Adjust the waste factor based on roof complexity. Simple gable roofs need 10%, complex roofs with valleys and dormers need 15-20%.
- Select your shingle type and enter local pricing to get cost estimates.
- Click 'Calculate' to see bundles, underlayment, starter strips, and all materials needed.
Why This Matters
Roofing materials are expensive, and running short means emergency trips to the supplier while your roof is exposed. Ordering too much wastes money on non-returnable materials. The pitch of your roof significantly affects the actual surface area - a 12/12 pitch roof has 41% more area than a flat roof of the same footprint.
- Calculate exact bundles needed with pitch-adjusted square footage
- Account for waste from cuts around vents, valleys, and edges
- Estimate all accessories: underlayment, drip edge, starter strips, ridge caps
- Get accurate cost estimates before starting your project
- Avoid running short on materials mid-installation
Worked Examples
Simple Gable Roof
A 30' × 40' home with a 6/12 pitch roof.
Complex Roof with Dormers
2,000 sq ft roof area with an 8/12 pitch and multiple dormers.
Steep Roof
1,500 sq ft footprint with a steep 12/12 pitch (45 degrees).
Common Mistakes to Avoid
- Forgetting to apply the pitch multiplier - a steeper roof needs significantly more material than the footprint suggests.
- Using house square footage instead of roof area - roof overhangs add 1-2 feet on each side.
- Not accounting for waste - valleys, hips, and cuts around vents all create waste.
- Ordering by the bundle instead of by the square - remember, 3 bundles = 1 square.
- Forgetting accessories - underlayment, starter strips, ridge caps, and nails add up.