Free calculator
Roof pitch calculator
A 6:12 pitch is 26.6°, a 50% slope, and multiplies the footprint by 1.118 to give the roof surface; 12:12 is 45° and multiplies it by 1.414. Type the rise per 12, the degrees, or a rise and a run in any unit, and the calculator gives the other forms, the multiplier, and the run and rise of a length measured along the slope.
Result
- Pitch
- 6:12
- Degrees
- 26.6°
- Slope (percent)
- 50%
- Area multiplier
- 1.118
Multiply the plan area (footprint) by the multiplier to get the roof surface. Geometry only: multiplier = the square root of 1 + (rise / run)². The last pitch is kept in this browser for the other calculators.
Ordering for the whole roof? Pro prints the materials list.
Every section with its area, the totals in bundles or tiles, underlayment, ridge, nails, drip edge, waste and the cost range, printable and as an Excel file.
How it works
Pitch is rise over run. In the US it is quoted per 12 units of run (6:12 means the roof rises 6 in for every 12 in across); in the UK it is quoted in degrees from the horizontal. Degrees = arctan(rise / run); percent = rise / run x 100; the area multiplier = the square root of 1 + (rise / run)², which is the length of the slope for one unit of run. Multiply the plan area of a roof section (the footprint) by the multiplier to get its surface, whatever the shape, as long as every slope has that pitch.
A length measured along the slope (eave to ridge on the surface) divided by the multiplier gives its horizontal run, and the run times rise / 12 gives its rise. These are geometry, not published figures, so this page cites no source for them; the pitch you type is kept in this browser for the other calculators.
| Pitch | Degrees | Slope | Area multiplier |
|---|---|---|---|
| 1:12 | 4.8° | 8.3% | 1.0035 |
| 2:12 | 9.5° | 16.7% | 1.0138 |
| 3:12 | 14° | 25% | 1.0308 |
| 4:12 | 18.4° | 33.3% | 1.0541 |
| 5:12 | 22.6° | 41.7% | 1.0833 |
| 6:12 | 26.6° | 50% | 1.118 |
| 7:12 | 30.3° | 58.3% | 1.1577 |
| 8:12 | 33.7° | 66.7% | 1.2019 |
| 9:12 | 36.9° | 75% | 1.25 |
| 10:12 | 39.8° | 83.3% | 1.3017 |
| 11:12 | 42.5° | 91.7% | 1.3566 |
| 12:12 | 45° | 100% | 1.4142 |
Frequently asked questions
- What is a 6:12 pitch in degrees?
- 26.57°: arctan(6 / 12). The reverse works too: type the degrees and the calculator gives the rise per 12. 4:12 is 18.4°, 8:12 is 33.7°, 12:12 is 45°.
- What is the roof pitch multiplier for?
- Roof surface = footprint x multiplier. A 1,000 sq ft footprint at 6:12 has 1,118 sq ft of roof; at 12:12 it has 1,414 sq ft. The shingle calculator and the tile calculator use the same multiplier on each section you type.
- How do I measure the pitch of my roof?
- In the attic, hold a level horizontally against a rafter, mark 12 in along it and measure the vertical distance from that mark up to the rafter: that is the rise per 12. On the roof, a pitch gauge or a phone inclinometer gives degrees. From the ground, count the rise and run on a gable end against the siding courses. Type whichever you have.
- Is a low pitch a problem for shingles or tiles?
- Every product has a minimum pitch on its data sheet. For the tiles in the tile calculator (Marley pages, read 2026-09-20): Modern 22.5° at 75 mm headlap and 17.5° smooth at 100 mm, Mendip 17.5° and 15°, Acme plain tiles 30°. Asphalt shingle makers set their own minimum and the underlayment method for low slopes. The calculator converts the pitch; the data sheet decides what can go on it.
- Rise and run are in metres, does that matter?
- No. Rise and run only need the same unit as each other: 1 m of rise over 2 m of run is 6:12 exactly. The slope length is the same: type it in any unit and the run and rise come back in that unit.