Select your starting point.
Use rise and run when you have measurements. Choose pitch ratio or angle when you already know one of those values.
Calculate roof pitch from rise and run, or convert a known pitch ratio or angle. Get the X:12 pitch, roof angle, slope percentage and slope multiplier in one place.
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A 6:12 pitch rises 6 units for every 12 horizontal units.
Estimates are for planning geometry only. This calculator does not assess roof loading, material suitability, structural design, drainage requirements or building-code compliance.
Use rise and run when you have measurements. Choose pitch ratio or angle when you already know one of those values.
Rise is vertical height. Run is horizontal distance. Both must use the same unit. Enter feet with feet or meters with meters.
Compare the pitch, angle, percentage and slope multiplier. Use the multiplier only for the corresponding roof plane and horizontal projected area.
This tool uses “pitch” in the common X:12 sense: vertical rise for every 12 units of horizontal run. Some technical references distinguish pitch as rise over total span, so check the convention used in your plans.
The slope multiplier converts a horizontal projected area into sloped surface area for a roof plane with a uniform slope. It does not add waste, overlaps or missing overhangs.
6 ÷ 12 = 0.5. The angle is approximately 26.57°, the slope is 50%, and the multiplier is approximately 1.1180. A 1,000 sq ft horizontal projected area at this uniform slope corresponds to about 1,118 sq ft of sloped roof area before waste.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 1:12 | 4.76° | 8.33% | 1.0035 |
| 2:12 | 9.46° | 16.67% | 1.0138 |
| 3:12 | 14.04° | 25% | 1.0308 |
| 4:12 | 18.43° | 33.33% | 1.0541 |
| 5:12 | 22.62° | 41.67% | 1.0833 |
| 6:12 | 26.57° | 50% | 1.1180 |
| 7:12 | 30.26° | 58.33% | 1.1577 |
| 8:12 | 33.69° | 66.67% | 1.2019 |
| 9:12 | 36.87° | 75% | 1.2500 |
| 10:12 | 39.81° | 83.33% | 1.3017 |
| 11:12 | 42.51° | 91.67% | 1.3566 |
| 12:12 | 45° | 100% | 1.4142 |
Values are rounded. These ratios are mathematical examples, not recommendations for a roofing material or building.
Understand the difference between pitch, slope, angle and horizontal run.
A 6:12 pitch means the roof rises 6 units for every 12 units of horizontal run. It is equivalent to a 50% slope and an angle of approximately 26.57°.
No. A 12:12 pitch has equal rise and horizontal run, which forms a 45° angle. Pitch notation and degrees describe the same slope in different ways.
Not necessarily. Run is the horizontal distance associated with the rise you measured. For a symmetrical gable roof, the wall-to-ridge run is usually half the relevant span. Overhangs and framing details must be handled consistently.
Convert them into one unit first. For example, 5 feet 6 inches equals 66 inches or 5.5 feet. Enter both rise and run using the same unit. Do not enter 5.6 to mean 5 feet 6 inches.
Take the tangent of the angle and multiply by 12. For example, tan(45°) × 12 = 12, so a 45° roof has a 12:12 pitch. The Angle mode performs this conversion.
No. A 100% slope means rise equals run, giving a 45° angle. A vertical surface has zero horizontal run, so its rise-to-run ratio is undefined.
No. It adjusts horizontal projected area for slope. Waste, cutoffs, laps and product-specific coverage must be calculated separately.
No. Material suitability depends on manufacturer requirements, the roof assembly, local rules and site conditions. Check those requirements with a qualified professional.