Free roofing tool
Roof Pitch & Area Calculator
Work out roof pitch, slope angle and multiplier, then turn your home's footprint into roof area, squares and shingle bundles.
Assumes a simple roof where all planes share one pitch. Ridge cap, starter strip and extra waste for many valleys are not included.
The Math Behind the Calculator
| Value | Formula | Units |
|---|---|---|
| Pitch (x/12) | rise ÷ run × 12 | inches of rise per 12 in. of run |
| Slope angle | arctan(rise ÷ run) | degrees |
| Rise from angle | tan(angle) × 12 | inches per 12 in. |
| Grade | rise ÷ run × 100 | percent |
| Slope multiplier | √(1 + (rise ÷ run)²) | unitless |
| Footprint | (length + 2 × overhang) × (width + 2 × overhang) | sq ft (overhang converted from in. to ft ÷ 12) |
| Roof area | footprint × slope multiplier | sq ft |
| Squares | roof area × (1 + waste %) ÷ 100 | 1 square = 100 sq ft |
| Bundles | squares × bundles per square, rounded up | bundles |
Common pitches at a glance
| Pitch | Angle | Multiplier | Typical use |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | Low-slope; needs special underlayment or membrane |
| 4/12 | 18.4° | 1.054 | Lowest common for shingles (with extra underlayment) |
| 6/12 | 26.6° | 1.118 | Very common on Central Texas homes |
| 8/12 | 33.7° | 1.202 | Steeper; more labor and safety equipment |
| 10/12 | 39.8° | 1.302 | Steep; specialty staging |
| 12/12 | 45.0° | 1.414 | 45°; very steep |
Ready to turn your measurements into a budget? Try the roof replacement cost calculator, or read about asphalt shingle and metal roofing options.
Roof Pitch FAQs
It means the roof rises 6 inches vertically for every 12 inches of horizontal run. Pitch is usually written as rise over a 12-inch run.
It is the factor that converts flat (plan-view) area into actual sloped roof surface: √(1 + (rise ÷ run)²). Multiply the footprint area by it to get roof area.
Most standard and architectural asphalt shingles are packaged three bundles per square (100 sq ft), but some heavier products use four or five. Check the specific product, and remember ridge cap and starter strips are usually ordered separately.
Yes. You can measure from inside the attic against a rafter, or at a gable end with a level and tape from a ladder at the eave — never on the roof surface. Many smartphone apps can also estimate pitch from a photo. If in doubt, a free inspection includes accurate measurements.
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Want Exact Roof Measurements? Book a Free Inspection.
Tell us what is going on with your roof and we will set up a time to take a look. The inspection is free, there is no obligation, and you will get clear answers either way.
- Photos of anything we find
- Repair-first, honest recommendations
- Written estimate if work is needed