Roof Pitch Calculator
This roof pitch calculator finds the pitch, the angle, and the rafter length of a roof from the rise and the run. Enter both and the roof pitch calculator returns the pitch as x in 12, the angle in degrees, and the slope. Use it to calculate a roof pitch, figure a roof slope, or convert a pitch to an angle.
Results
The Roof Pitch Calculator is part of our Structural collection. Browse more structural to size, convert, and check your work alongside this tool.
What the roof pitch calculator shows
Roof pitch is how steep a roof is, given as the rise over a 12 unit run. This roof pitch calculator turns a rise and run into the pitch as x in 12, the angle in degrees, and the rafter length. As a roof slope calculator and a roof pitch estimator it gives every form of the steepness at once, so you can read it whichever way your job needs.
How to calculate a roof pitch
To calculate a roof pitch, the roof pitch calculator works the rise and run three ways:
The pitch expresses the rise per 12 of run, the angle is the same slope in degrees, and the slope multiplier scales a flat area up to the true roof area. Figuring roof pitch this way gives all three from one rise and run.
Roof pitch calculator example
A roof that rises 4 over a run of 12. The roof pitch calculator gives:
The slope multiplier is about 1.054, and a rafter over that span is √(4² + 12²) = 12.65 long. Change the rise and the roof pitch calculator updates all three at once.
How to use the roof pitch calculator
Enter the rise and the run in the same units, then the roof pitch calculator returns the pitch, the angle, and the slope. The rise is the vertical height and the run is the horizontal distance; using 12 for the run gives the pitch directly as x in 12. To calculate a roof pitch from a measured rise over a known run, the roof gradient calculator does the rest.
Reading the roof slope calculator result
The pitch as x in 12 is the builder shorthand; the angle in degrees suits drawings and cutting; and the slope multiplier turns the flat footprint into the real sloped area for ordering materials. A low slope roof, under about 3 in 12, needs different roofing than a steep one. Use the angle to set a saw, the pitch to order trusses, and the multiplier to size the roofing, all from the same rise and run the roof pitch calculator uses.
When to use the roof pitch estimator
- Setting truss or rafter pitch with the roof pitch estimator
- Converting a pitch to an angle for cutting
- Figuring a roof slope for a shed with a shed roof pitch calculator
- Sizing roofing with the slope multiplier
Common roof pitch calculator mistakes
- Using footprint area for roofing. Multiply by the slope multiplier to get the true sloped area.
- Mixing rise and run units. Both must be in the same unit for the angle to come out right.
- Confusing pitch and angle. Pitch is x in 12; the angle is the same slope in degrees.
Tips for measuring a roof
- Measure the rise over a level 12 inch run for the pitch directly.
- Use the angle to set a saw and the pitch to order trusses.
- Scale the flat area by the multiplier before ordering roofing.
Figuring roof pitch and roof slope
Figuring roof pitch and figuring roof slope are the same measurement in different words: both describe how far the roof rises over a horizontal run. Builders quote it as x in 12, so a 6 in 12 roof rises 6 for every 12 across, while engineers and saw setups prefer the angle in degrees. To calculate pitch on a roof you can measure the rise over a level 12 inch run at the eave, or read the rise and run off the plans. A roof gradient calculator and a pitch of the roof calculator return the same numbers; the only choice is which form you read. Once you have the pitch, converting to degrees is a single arctangent, which is why the roof pitch calculator shows both.
Degrees of roof pitch and the roof pitch multiplier
The degrees of roof pitch matter for cutting and for comparing roofs, while the roof pitch multiplier matters for ordering materials. The multiplier is the slope length divided by the run, so a steeper roof has more actual surface than its flat footprint suggests: a 12 in 12 roof at 45 degrees has 1.414 times the footprint area. Multiply the flat plan area by the multiplier and you get the true roof area to shingle, which is exactly how the roofing calculator turns a footprint into a materials order. A roof slope multiplier that is ignored leaves a steep roof short on shingles, so always scale the flat area up by it.
Roof pitch multiplier chart
Angle and slope multiplier by pitch, a quick roof pitch multiplier chart for the roof pitch calculator:
| Pitch | Angle | Slope multiplier |
|---|---|---|
| 3 in 12 | 14.0° | 1.031 |
| 4 in 12 | 18.4° | 1.054 |
| 6 in 12 | 26.6° | 1.118 |
| 9 in 12 | 36.9° | 1.25 |
| 12 in 12 | 45.0° | 1.414 |
Roof Pitch Calculator FAQ
How do you calculate a roof pitch?
Divide the rise by the run and multiply by 12 for the pitch as x in 12, and take the arctangent of rise over run for the angle. The roof pitch calculator does both.
How do I convert roof pitch to degrees?
Take the arctangent of the rise over the run. A 4 in 12 pitch is about 18.4 degrees, and the roof pitch calculator shows the degrees of roof pitch directly.
What is the roof pitch multiplier?
It is the factor that turns the flat footprint into the true sloped area, equal to the slope length over the run. A 6 in 12 roof has a multiplier of about 1.118.
How do I figure the pitch of a shed roof?
Measure the rise across a known run and enter both. A shed roof pitch calculator uses the same rise over run, often a lower slope than a house roof.