Roof Pitch Calculator

Enter the rise and run of the roof or the angle in degrees to calculate the pitch. Learn more about finding the rise and run of the angle below.

How to Calculate the Pitch of a Roof

Homes and other buildings have roofs with slopes ranging from no slope or flat to very steep slopes. Roof pitch is used to describe the slope, or angle, of the roof. The roof pitch is important in determining the appropriate installation method and how much roofing material will be needed.

Roof pitch, or slope, is a measure of vertical rise to horizontal run expressed in inches per foot.[1] A roof with a 6″ rise for every 12″ run has a 6″ per foot, or 6 in 12 pitch.

Pitch is thus the ratio of the rise in inches to a 12-inch run, and is often expressed using a semicolon, for example 6:12. Sometimes pitch is also expressed in fraction form using a fraction with a slash, such as 6/12.

Finding the pitch of a roof can be done by finding the rise and run, or converted from the angle if it is known. See the chart below for some examples of common roof pitches.

Roof pitch is a measure of the angle of a roof and is expressed as the rise over a 12 inch run.

Method One: Measure From the Roof

One method to find the pitch is to climb on the roof and measure the rise for a 12″ run. You’ll need a level that is 12″ or longer and a tape measure.

On the roof, hold the level perfectly level, and measure the height from the roof to the level 12 inches away from where the level touches the surface, this will be the rise.

For example, if the level is 4″ above the roof at a point 12″ away from where the level is touching the surface, then the pitch is 4:12.

Find the pitch of a roof using a level and tape measure and measuring the rise over run

Method Two: Measure From the Attic

Another method to find the roof pitch is to go into the attic and measure the rise for a 12″ run of the roof rafters, which allows finding the pitch without going on the roof.

From the attic, hold a level perfectly level and touching a rafter at one end. Measure the distance from the level to the rafter 12 inches away from where the level touches the rafter.[2]

You can also find the pitch of a roof from the attic using a level and tape measure

Method Three: Measure the Total Rise and Run

If you know the total height of the peak and the width of the roof you can also find the pitch with a little math. For example, if the peak is 4 feet and the total roof with is 20 feet, the total rise is 4 feet, or 48 inches.

The total run is the distance from the peak to the edge of the roof, which in this case is the total width divided in half, which is equal to 10 feet or 120 inches. Since pitch is the rise over a 12 inch run, divide the run by 12 to get the multiplier, in this case 120 ÷ 12 = 10.

Now, divide the rise by the multiplier to get the pitch, eg. 48 ÷ 10 = 4.8. The pitch of this roof is 4.8:12. The calculator above can handle much of this math.

You can also find the roof pitch by using the total rise and total run and reduce to a rise over a 12 inch run.

Method Four: Measure With a Speed Square

A speed square and level can be used to easily find the pitch of a roof. Set the level on the edge of the speed square as shown below then place the heel of the speed square on a rafter or gable edge of the roof.

Holding the level and speed square level, locate the measurement on the speed square where it meets the bottom edge of the rafter to find the angle of the roof in degrees.

Locating roof pitch in degrees using a speed square and level

How to Convert Angle in Degrees to Roof Pitch

If you know the angle of the roof in degrees you can find the roof pitch by converting the angle in degrees to a slope, then finding the rise by multiplying the slope by 12.

First, find the slope by finding the tangent of the degrees, eg. slope = tan(degrees). Then multiply the slope by 12 to get the rise. The pitch is expressed as inches per foot.

Example: let’s find the pitch for a roof angle of 35°.

tan(35) = 0.7002
0.7002 × 12 = 8.4025
Pitch = 8.4:12

How to Convert Roof Pitch to Degrees

To find the angle of a roof in degrees convert the pitch to a slope, then convert to degrees by finding the arc tangent of the slope. First, convert the pitch to a slope.

To do this simply convert the rise and run as a fraction to a decimal form, eg. rise/run = rise ÷ run = slope. For a pitch expressed in inches per foot, convert to a fraction first, eg. a 4 in 12 pitch becomes 4/12, then divide.

Next, find the degrees by finding the arc tangent of the slope, eg. degrees = atan(slope).

Example: let’s find the angle in degrees for a roof with a 4 in 12 pitch.

4:12 = 4 ÷ 12 = .333
atan(.333) = 18.4178
Angle = 18.4°

Learn more about finding the angle of a line using our slope calculator.

Common Roof Pitches and Equivalent Grade, Degree, and Radian Angles

Most roof’s have a pitch in the 4:12 to 9:12 range. A pitch over 9:12 is considered a steep-slope roof, between 2:12 and 4:12 is considered a low-slope roof, and less than 2:12 is considered a flat roof.[3] The table below shows common roof pitches and the equivalent grade, degrees, and radians for each.

The equivalent grade, degrees, and radians for common roof pitches.
Pitch Grade (slope) Degrees Radians
1/8:12 1% 0.6° 0.01
1/4:12 2.1% 1.2° 0.02
1/2:12 4.2% 2.4° 0.04
1:12 8.3% 4.8° 0.1
2:12 16.7% 9.5° 0.2
3:12 25% 14° 0.2
4:12 33.3% 18.4° 0.3
5:12 41.7% 22.6° 0.4
6:12 50% 26.6° 0.5
7:12 58.3% 30.3° 0.5
8:12 66.7% 33.7° 0.6
9:12 75% 36.9° 0.6
10:12 83.3% 39.8° 0.7
11:12 91.7% 42.5° 0.7
12:12 100% 45° 0.8
13:12 108.3% 47.3° 0.8
14:12 116.7% 49.4° 0.9
15:12 125% 51.3° 0.9
16:12 133.3% 53.1° 0.9
17:12 141.7% 54.8° 1
18:12 150% 56.3° 1
19:12 158.3% 57.7° 1
20:12 166.7% 59° 1
21:12 175% 60.3° 1.1
22:12 183.3% 61.4° 1.1
23:12 191.7% 62.4° 1.1
24:12 200% 63.4° 1.1

Roofing Cost

If you’re considering a new roof we suggest getting several estimates to learn more about the right roofing system for your roof pitch and understand the cost of installation. We also cover more about roof replacement cost in detail in our cost guide.

References

  1. Nick Gromicko and Benjamin Gromicko, Measuring Roof Slope and Pitch, International Association of Certified Home Inspectors, https://www.nachi.org/roof-slope-pitch.htm
  2. SFGate, How to Measure Roof Slope Angles, https://homeguides.sfgate.com/measure-roof-slope-angles-26885.html
  3. Evan Gillespie, What Is the Standard Roof Pitch?, Hunker, https://www.hunker.com/13401081/what-is-the-standard-roof-pitch