Tools
Roof Calculator
Find your roof's size, pitch, how many shingles to buy, and a rough replacement cost. Free, instant, and no phone number needed.
Developed by AssistQuote
Measurements follow standard roofing estimating tables. Not a quote or an estimate from a contractor.
Your results
Enter your home's size
Based on about $4.40–$11.00 per square foot (Angi, 2026). Not a quote. Material, tear-off, rotten decking and your area can change the price a lot.
How this calculator works
- It finds your roof's "plan" area. That's your home's length times width, plus the overhang on each side.
- It adjusts for slope. A sloped roof has more surface than the ground under it. A 6/12 roof has about 12% more. A 12/12 roof has about 41% more.
- It adds waste. Roofers order extra for cuts: about 10% for a gable roof and 15% for a hip roof.
- It converts to squares and bundles. One "square" is 100 square feet. Most shingles come about 3 bundles to a square.
Roof pitch multipliers
| Pitch | Angle | Multiply plan area by |
|---|---|---|
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 5/12 | 22.6° | 1.083 |
| 6/12 | 26.6° | 1.118 |
| 7/12 | 30.3° | 1.158 |
| 8/12 | 33.7° | 1.202 |
| 9/12 | 36.9° | 1.250 |
| 10/12 | 39.8° | 1.302 |
| 12/12 | 45.0° | 1.414 |
Good to know
- This is an estimate. Dormers, valleys, skylights and multiple roof levels add area and waste. A roofer will measure exactly.
- Stay off the roof. You can measure from the ground or in the attic. Leave climbing to the pros.
- Cost varies a lot. Material, tearing off old layers, rotten decking and your area can move the price well outside this range.
Questions people ask
Divide your roof's area in square feet by 100. A 1,500 sq ft roof is 15 squares.
Most shingles come 3 bundles per square. Add 10–15% for waste. The calculator does this for you.
Measure how many inches the roof rises over 12 inches of level run. A roof that rises 6 inches over 12 is a 6/12 pitch. Use the pitch tab above.
About $4.40 to $11.00 per square foot of roof, based on Angi's 2026 data. A new roof averages about $9,609.