Roof Pitch Calculator
Enter the rise and run to instantly convert your roof pitch into the X-in-12 ratio, the angle in degrees, the percentage grade and the 1-in-N gradient, with a dimensioned angle diagram and a full pitch chart.
Roof pitch (rise in 12)
6:12
Rise per 12 units of run
- Angle
- 26.6°
- Percentage grade
- 50.0%
- Gradient
- 1 in 2.00
- Slope factor
- 1.1180
From horizontal
Sloped length per unit run
Dimension diagram
About this roof pitch calculator
This roof pitch calculator converts the slope of a roof between every common format: the X-in-12 ratio builders use, the angle in degrees, the percentage grade, and the "1 in N" gradient. Enter the rise and the run in the same unit and it returns all of them at once, plus a dimensioned angle diagram and a full pitch reference chart. It is built for roofers, builders and DIYers who need to read, convert or double-check a roof slope. Every figure is plain trigonometry on the rise and run you enter, so it can be checked by hand. If you instead need the length of the rafter to cut for a given pitch, use the rafter calculator.
Once you know the pitch and need the length of the rafter to cut for it, switch to our rafter length calculator for the rafter length, plumb and seat cut angles, birdsmouth and a cut list.
How to measure roof pitch
- 1
Measure the run
The run is the horizontal distance under the slope. For the X-in-12 ratio, use a run of 12 (inches). To measure an existing roof, hold a level out horizontally from the roof surface and measure 12 inches along it.
- 2
Measure the rise
The rise is the vertical height the roof climbs over that run. From the 12-inch mark on your level, measure straight down to the roof surface. That vertical distance in inches is your rise (the "x" in x-in-12).
- 3
Enter rise and run in the same unit
Type the rise and run into the calculator using the same unit for both (they form a ratio, so the unit cancels out). The default 6 and 12 describes a 6-in-12 roof.
- 4
Read every pitch format
The calculator returns the pitch as an X:12 ratio, the roof angle in degrees, the percentage grade, the 1-in-N gradient, and the slope factor used to estimate sloped length from a horizontal run.
- 5
Use the pitch reference chart
Scan the reference chart to look up how any common pitch (1-in-12 through 12-in-12) converts to degrees and percentage, or to match a measured angle back to the nearest standard pitch.
Roof pitch chart
Look up how every common roof pitch converts to an angle in degrees, a percentage grade and a 1-in-N gradient, or match a measured angle back to the nearest standard pitch.
| Pitch | Angle | Percentage | Gradient |
|---|---|---|---|
| 0.5:12 | 2.4° | 4.2% | 1 in 24.00 |
| 1:12 | 4.8° | 8.3% | 1 in 12.00 |
| 1.5:12 | 7.1° | 12.5% | 1 in 8.00 |
| 2:12 | 9.5° | 16.7% | 1 in 6.00 |
| 3:12 | 14.0° | 25.0% | 1 in 4.00 |
| 4:12 | 18.4° | 33.3% | 1 in 3.00 |
| 5:12 | 22.6° | 41.7% | 1 in 2.40 |
| 6:12 | 26.6° | 50.0% | 1 in 2.00 |
| 7:12 | 30.3° | 58.3% | 1 in 1.71 |
| 8:12 | 33.7° | 66.7% | 1 in 1.50 |
| 9:12 | 36.9° | 75.0% | 1 in 1.33 |
| 10:12 | 39.8° | 83.3% | 1 in 1.20 |
| 11:12 | 42.5° | 91.7% | 1 in 1.09 |
| 12:12 | 45.0° | 100.0% | 1 in 1.00 |
Frequently asked questions
How do I calculate roof pitch?
Roof pitch is the rise divided by the run. To express it as the common X-in-12 ratio, multiply rise ÷ run by 12. To get the angle in degrees, take the arctangent of rise ÷ run. To get the percentage grade, multiply rise ÷ run by 100. This calculator does all three from the rise and run you enter.
What is a 6/12 roof pitch in degrees?
A 6-in-12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. Its angle is arctan(6 ÷ 12) = 26.57°, and its percentage grade is 50%. You can confirm this and any other pitch in the reference chart on this page.
What is the difference between roof pitch, slope and gradient?
They describe the same steepness in different formats. Pitch is usually written as an X-in-12 ratio, slope is often expressed as the angle in degrees or as a percentage grade, and gradient is written as "1 in N" (one unit of rise for every N units of run). This calculator shows all of them together so you can convert between them.
How do I convert roof pitch to an angle?
The roof angle equals the arctangent of the pitch expressed as rise over run: angle = arctan(rise ÷ run). For an X-in-12 pitch, that is arctan(x ÷ 12). For example a 4-in-12 pitch is arctan(4 ÷ 12) = 18.43°.
How do I convert a roof angle back to an X-in-12 pitch?
Take the tangent of the angle and multiply by 12: pitch = tan(angle) × 12. For example a 30° roof is tan(30°) × 12 = 6.93, which rounds to a 7-in-12 pitch. The reference chart lists the exact angle for each standard pitch so you can match a measured angle to the nearest one.
What is the minimum roof pitch?
The minimum usable pitch depends on the roofing material and the manufacturer and code requirements, and low-slope roofs use different products than steep-slope roofs. Because the allowable minimum is set by your roofing material and local building code, check those for your specific project rather than relying on a single number.
What does "1 in N" roof gradient mean?
A "1 in N" gradient means the roof rises 1 unit for every N units of horizontal run. It is another way of writing the slope: N equals run ÷ rise. For example a 6-in-12 pitch is a 1-in-2 gradient, and a 3-in-12 pitch is a 1-in-4 gradient.
Does this calculator give the rafter length?
No — this page focuses on converting the roof pitch itself. It does report the slope factor (sloped length per unit of run), but to get the actual rafter length to cut, along with the plumb and seat cut angles, birdsmouth and a cut list, use the rafter calculator.
Is roof pitch measured in inches or degrees?
Both are used. In the United States roof pitch is most often written as an X-in-12 ratio (inches of rise per 12 inches of run), while the angle in degrees and the percentage grade are common elsewhere and in engineering. This tool converts between all of them at once.
Roof pitch terms glossary
- Roof pitch
- The steepness of a roof, most often written as rise in inches per 12 inches of horizontal run (for example 6-in-12).
- Run
- The horizontal distance under the roof slope; a run of 12 inches is the basis of the X-in-12 ratio.
- Rise
- The vertical height the roof climbs over the run; the "x" in an x-in-12 pitch.
- Slope (degrees)
- The roof angle measured from horizontal, equal to arctan(rise ÷ run).
- Percentage grade
- The slope written as a percentage, equal to rise ÷ run × 100.
- Gradient (1 in N)
- The slope written as 1 unit of rise per N units of run, where N = run ÷ rise.
- Slope factor
- The multiplier √(rise² + run²) ÷ run that converts a horizontal run into sloped length.