Roofing Calculator
Turn a building footprint and roof pitch into roof area, roofing squares and shingle bundles, with waste included. Then download or print a clean summary for your estimate.
- Any pitch
- Squares & bundles
- PDF summary
Your roof
Measure the footprint including the overhangs (eaves and rakes).
For more than one roof plane at different pitches, calculate each section separately and add them up.
Your materials
Updates as you type. Bundles are rounded up.
How to Calculate Roof Area and Roofing Squares
You can estimate a roof from the ground. Measure the building's footprint including the overhangs, then use the roof pitch to convert that flat area into the real, sloped surface area. Divide by 100 to get roofing squares, the unit shingles and roofing labor are priced in.
Roofing Formulas
Pitch Multiplier Table
| Pitch | Multiplier | 1,000 sq ft footprint becomes |
|---|---|---|
| 3/12 | 1.031 | 1,031 sq ft |
| 4/12 | 1.054 | 1,054 sq ft |
| 5/12 | 1.083 | 1,083 sq ft |
| 6/12 | 1.118 | 1,118 sq ft |
| 7/12 | 1.158 | 1,158 sq ft |
| 8/12 | 1.202 | 1,202 sq ft |
| 9/12 | 1.250 | 1,250 sq ft |
| 10/12 | 1.302 | 1,302 sq ft |
| 12/12 | 1.414 | 1,414 sq ft |
Worked Example: a 40 × 30 ft Gable Roof
A house measuring 40 × 30 ft including overhangs, with a 6/12 pitch, 10% waste and shingles at 3 bundles per square:
Starter strip, hip and ridge caps are often bought separately, by the linear foot of eave, hip and ridge. Check your shingle manufacturer's coverage for those accessories.
Waste Allowance by Roof Type
- Simple gable roof: about 10%.
- Hip roof: about 15%, because every hip needs cut shingles.
- Complex roofs with valleys, dormers and multiple planes: 15–20% or more.
Roofs with several sections at different pitches are best calculated section by section, then added together.
From Squares to a Profitable Roofing Quote
Shingles are only part of a roofing estimate. A quote that makes money also covers tear-off and disposal, underlayment, flashing, drip edge, vents, labor per square, equipment, overhead and profit:
- Price your crew at their true cost with the employee cost calculator
- Recover your fixed costs with the overhead calculator
- Set your price with the markup calculator
- Send good, better and best options with roofing estimating software