Roofing Square Footage Calculator
Accurately estimate the total square footage and number of roofing "squares" needed for your project.
Flat (0/12)
1/12
2/12
3/12
4/12
5/12
6/12
7/12
8/12
9/12
10/12
11/12
12/12 (45°)
10% (Standard Gable)
15% (Hip Roof)
20% (Complex/Valleys)
Ground Footprint Area:
0 sq ft
Actual Roof Surface Area:
0 sq ft
Area with Waste Factor:
0 sq ft
Roofing Squares Needed:
0 Squares
*1 Roofing Square = 100 Square Feet of material.
How to Calculate Roofing Square Footage
Calculating the area of a roof is more complex than a standard floor plan because of the pitch (slope). A roof with a steep incline has significantly more surface area than a flat roof covering the same building footprint.
The Formula for Roofing Squares
To find the total area, we use the building's base dimensions and apply a "Pitch Factor" (a multiplier based on the Pythagorean theorem). The basic steps are:
- Calculate Base Area: Length × Width of the building footprint.
- Apply Pitch Factor: Multiply the Base Area by the Pitch Multiplier (e.g., a 6/12 pitch has a multiplier of 1.158).
- Add Waste: Roofing involves cutting shingles at valleys and edges. Add 10% to 15% to ensure you don't run out of material.
- Convert to Squares: Divide the final square footage by 100.
Example Calculation
Suppose you have a house that is 30 feet wide and 40 feet long with a 6/12 pitch:
- Base Area: 30 × 40 = 1,200 sq ft.
- Pitch Adjustment: 1,200 × 1.158 = 1,389.6 sq ft.
- Waste Factor (10%): 1,389.6 × 1.10 = 1,528.56 sq ft.
- Total Squares: 1,528.56 / 100 = 15.29 Squares.
Understanding Roof Pitch
Roof pitch is expressed as a ratio of "Rise over Run." A 4/12 pitch means the roof rises 4 inches for every 12 inches it runs horizontally. The steeper the pitch, the higher the multiplier. Using this calculator helps you avoid manual trigonometry and ensures you order the correct amount of shingles, underlayment, and drip edge.