Roof Area Calculator Formula
Understand the math behind the roof area calculator. Each variable explained with a worked example.
Formulas Used
Footprint Area
footprint_sqft = footprint_areaPitch Factor
pitch_mult = pitch_factorRoof Surface Area
roof_area = footprint_area * pitch_factorRoofing Squares
roofing_squares = footprint_area * pitch_factor / 100Variables
| Variable | Description | Default |
|---|---|---|
footprint_length | Building Length(feet) | 50 |
footprint_width | Building Width(feet) | 30 |
pitch_rise | Pitch Rise (per 12 in run)(inches) | 6 |
footprint_area | Derived value= footprint_length * footprint_width | calculated |
pitch_factor | Derived value= sqrt(1 + pow(pitch_rise / 12, 2)) | calculated |
How It Works
How to Calculate Roof Area
Formula
Roof Area = Footprint Area × Pitch Factor
Pitch Factor = sqrt(1 + (Rise/12)²)
| Pitch | Factor | |-------|--------| | 4/12 | 1.0541 | | 5/12 | 1.0833 | | 6/12 | 1.1180 | | 8/12 | 1.2019 | | 10/12 | 1.3017 | | 12/12 | 1.4142 |
This method converts the horizontal footprint into the actual surface area by accounting for the roof slope.
Worked Example
A building 50 ft by 30 ft with a 6/12 roof pitch.
footprint_length = 50footprint_width = 30pitch_rise = 6
- 01Footprint area = 50 × 30 = 1,500 sq ft
- 02Pitch factor = sqrt(1 + (6/12)²) = sqrt(1.25) = 1.1180
- 03Roof area = 1,500 × 1.1180 = 1,677 sq ft
- 04Roofing squares = 1,677 / 100 = 16.8 squares
Ready to run the numbers?
Open Roof Area Calculator