Roofing Calculator
Estimate your total roof area, pitch multiplier, and material costs instantly. Enter your home's base footprint below to get started.
Results
Shingle & Material Estimator
Enter your total roof area below to see how many bundles of shingles you need.
Material Requirements
How to Use This Calculator
- Enter Base Area: Input the ground-floor footprint of your home (Length × Width). Do not try to guess the roof slope yet; the calculator handles that.
- Select Roof Pitch: Choose the pitch from the dropdown menu (e.g., 4/12). If you don't know it, 4/12 or 5/12 are common for standard homes.
- Add Eaves (Overhang): Enter how far your roof hangs over the wall (typically 1 to 2 feet). This adds significant area to the final total.
- Price (Optional): If you know the cost per square foot of materials or labor, enter it to get a total cost estimate.
- Click Calculate: The tool will provide the total roof area and the number of "Squares" (100 sq ft units).
Complete Guide to Roofing Calculations
Whether you are a DIY homeowner or a contractor, accurate roof measurements are essential to avoid overspending on materials or running short during a job. The Calculatorbudy Roofing Calculator helps you convert your home's ground-level footprint into the actual surface area of the roof, accounting for slope and overhangs.
Understanding Roof Pitch (Slope)
The "Pitch" is the incline of the roof. It is defined as the vertical rise (in inches) for every 12 inches of horizontal run. A steeper roof has a larger surface area than a flat roof covering the same house.
| Pitch Ratio | Approximate Angle | Roof Type |
|---|---|---|
| 1/12 to 3/12 | 4.5° - 14° | Low Slope |
| 4/12 to 9/12 | 18° - 37° | Medium Slope (Walkable) |
| 10/12 to 12/12 | 40° - 45° | Steep Slope (Safety Gear Needed) |
| 18/12+ | 56°+ | Mansard / Very Steep |
How to Calculate Roof Waste Factor
- Simple Gable Roofs: Add 5-7% waste.
- Standard Hip Roofs: Add 10-12% waste.
- Complex Roofs (Dormers/Valleys): Add 15-20% waste.
Roofing Material Terms
- Square: A standard unit in the roofing industry. 1 Square = 100 square feet.
- Bundle: Asphalt shingles are sold in bundles. Typically, 3 bundles cover 1 Square (approx. 33.3 sq ft per bundle).
- Underlayment: The waterproof barrier installed directly on the deck. It is usually sold in rolls of 4 squares (400 sq ft) or 10 squares (1000 sq ft).
- Linear Footage (Ridge/Hip): Don't forget to measure the length of ridges and hips separately for capping shingles.
The Math Behind the Calculator
If you want to calculate this manually, you need the Pythagorean Theorem. The roof acts as the hypotenuse of a triangle.
Formula:Roof Area = Base Area × Pitch Multiplier
For example, a 6/12 pitch has a multiplier of approximately 1.118. If your house footprint (plus eaves) is 2,000 sq ft, the roof area is: 2000 × 1.118 = 2,236 sq ft.
Frequently Asked Questions
Measure the length and width of your house's base footprint. Multiply them to get the base area. Then, use our calculator to apply the 'pitch multiplier' (based on the roof's steepness) and add the eaves overhang.
In the roofing industry, a "Square" is a standard unit of measurement equal to 100 square feet. Contractors and suppliers quote prices per square rather than per square foot.
Typically, there are 3 bundles of standard asphalt shingles in one Square (approx. 33.3 sq ft per bundle). Heavier architectural shingles may require 4 bundles per square.