Work out roof pitch, angle and slope from rise and run, then estimate squares and shingle bundles.
Walkable
Enter the rise and run (or an angle) to get your pitch, angle, slope and pitch multiplier. Add your footprint to see the real roof area, how many squares you need with waste, and how many bundles of shingles to buy.
You don't need to climb onto the roof. From inside the attic or at the gable end, hold a level horizontally against the underside of a rafter and mark 12 inches along the level. At that mark, measure straight up to the rafter. That vertical distance in inches is your rise, so 6 inches means a 6/12 pitch. On the roof itself, the same method works with the level resting on the shingles. For a quick check you can also measure the rafter angle with a phone inclinometer app and use angle mode.
Pitch is the rise for every 12 inches of run, and every other number comes from that ratio. The multiplier tells you how much bigger the sloped roof is than its flat footprint.
The multiplier works for simple gable and hip roofs where every face has the same pitch. For dormers, valleys or sections at different pitches, calculate each section separately and add them.
Rise 6 in, run 12 in, footprint 2,000 sq ft, 10% waste. The pitch is 6/12, the angle is 26.57°, the slope is 50%, and the multiplier is √1.25, about 1.1180. Roof area = 2,000 × √1.25 = 2,236.1 sq ft (the tool uses the unrounded multiplier, 1.118034…), or 22.36 squares. With 10% waste that's 24.60 squares, so you'd buy 74 bundles.
Rise 4, run 12, footprint 1,500 sq ft, 10% waste. Angle 18.43°, slope 33.33%, multiplier 1.0541. Roof area is 1,581.1 sq ft (15.81 squares), or 17.39 squares with waste.
A rise of 30 in over a run of 60 in is the same ratio as 6 over 12, so it's also a 6/12 pitch at 26.57°.
A 30° roof is 12 × tan(30°) = 6.93/12, which is close to a standard 7/12.
| Pitch | Angle | Slope | Multiplier |
|---|---|---|---|
| 1/12 | 4.76° | 8.33% | 1.0035 |
| 2/12 | 9.46° | 16.67% | 1.0138 |
| 3/12 | 14.04° | 25.00% | 1.0308 |
| 4/12 | 18.43° | 33.33% | 1.0541 |
| 5/12 | 22.62° | 41.67% | 1.0833 |
| 6/12 | 26.57° | 50.00% | 1.1180 |
| 7/12 | 30.26° | 58.33% | 1.1577 |
| 8/12 | 33.69° | 66.67% | 1.2019 |
| 9/12 | 36.87° | 75.00% | 1.2500 |
| 10/12 | 39.81° | 83.33% | 1.3017 |
| 11/12 | 42.51° | 91.67% | 1.3566 |
| 12/12 | 45.00° | 100.00% | 1.4142 |
About 10% covers a simple gable roof. Hip roofs and roofs with valleys, dormers, or lots of cuts usually need around 15%. Starter strips and ridge caps are often bought separately, so check those with your supplier.
A 6/12 pitch is 26.57°. The roof rises 6 inches for every 12 inches of horizontal run, a 50% slope.
They describe the same steepness. Pitch is usually written as rise over 12 (like 6/12), while slope is often written as a percentage (50%) or an angle (26.57°).
It's the factor that converts a flat footprint into actual sloped roof area, √(1 + (rise/run)²). For a 6/12 roof it's 1.1180, so a 2,000 sq ft footprint has about 2,236 sq ft of roof.
Multiply the footprint (including overhangs) by the pitch multiplier, divide by 100, and add waste. A 2,000 sq ft footprint with a 6/12 roof and 10% waste needs about 24.6 squares.
Yes. Measure the outside edges of the eaves and rakes, not the walls, or you'll come up short.
In this calculator, 2/12 and below is labeled low slope, where standard shingles usually aren't recommended. 8/12 and above is labeled steep, which typically needs extra safety gear to work on.
Use it section by section. Calculate each plane or wing with its own pitch and footprint, then add the results.