Roofing calculator for area, pitch, squares and bundles
Enter footprint dimensions, pitch and waste. HitEquals converts plan area to sloped roof area, roofing squares, bundle count and underlayment rolls with your product coverage.
Inputs used by this calculator
Roofing Calculator uses the fields below. The starting values reproduce the page example; replace them with values from the same units and time period before using the result.
| Input | Starting example | Accepted value | How it is used |
|---|---|---|---|
| Length unit | Feet | Feet · Meters | Selects the unit or conversion path used by Roofing Calculator. |
| Building length | 40 | 0.01 to 1000000 | Supplies the building length quantity used by the published equation or result breakdown. |
| Building width | 30 | 0.01 to 1000000 | Supplies the building width quantity used by the published equation or result breakdown. |
| Roof rise per 12 units of run | 6 | 0 to 1000 | Selects the unit or conversion path used by Roofing Calculator. |
| Waste allowance (%) | 10 | 0 to 100 | Supplies the waste allowance (%) quantity used by the published equation or result breakdown. |
| Coverage per shingle bundle (ft²) | 33.3 | 0.01 to 1000000 | Supplies the coverage per shingle bundle (ft²) quantity used by the published equation or result breakdown. |
| Coverage per underlayment roll (ft²) | 400 | 0.01 to 10000000 | Supplies the coverage per underlayment roll (ft²) quantity used by the published equation or result breakdown. |
Footprint and sloped area
The footprint is length times width viewed from above. Pitch increases the actual surface along the slope.
Roof pitch formulas
A rise-per-12 pitch forms a right triangle with run 12. Dividing the hypotenuse by 12 gives the multiplier.
slope factor=√(144+rise²)/12roof area=length×width×slope factororder area=roof area×(1+waste%)Worked 6:12 example
For 6:12 pitch, the factor is √180/12≈1.118. A 1,200 ft² footprint therefore has about 1,341.64 ft² of sloped surface.
Roofing squares and bundles
One roofing square is 100 square feet. Bundle coverage varies, so enter the printed product coverage rather than assuming exactly three bundles per square.
What the estimate omits
Complex roof planes, overhangs, valleys, hips, ridges, dormers and penetrations need direct measurements and accessory quantities.
Safety and professional takeoff
Roof work has serious fall and structural hazards. Use plans or safe measurement methods and have ordering and installation checked by qualified professionals.
Common pitch factors
| Pitch | Factor |
|---|---|
| 0:12 | 1.000 |
| 4:12 | 1.054 |
| 6:12 | 1.118 |
| 8:12 | 1.202 |
| 12:12 | 1.414 |
Frequently asked questions
What is a roofing square?
It is 100 square feet of roof area.
Why does pitch increase area?
The sloped surface is longer than its horizontal projection.
Are overhangs included?
Only if the entered footprint dimensions include them.
How many bundles are in a square?
Product coverage varies; enter the bundle's labeled square-foot coverage.
Does this handle dormers and valleys?
No. Add their measured planes and accessories separately.
Can I use meters?
Yes. Geometry is converted to square feet for product counts and also reported in square meters.
What to keep in mind
This geometric estimate assumes one uniform pitch over the entered footprint. Valleys, hips, dormers, overhangs, openings, starter strips, ridge materials and product-specific coverage require a measured takeoff.
Results are rounded for display in US format, with money in dollars and cents; CSV exports keep full calculation precision. This is a calculation summary, not an official certificate.