Use a level against the underside of the rafter you re measuring to get the most accurate value.
How to work out the slope of a roof.
Recalculate this value into an angle.
Calculate the roof pitch as the proportion of rise and run.
Calculating roof slope is done by calculating the number of inches your roof slope rises vertically for every 12 inches it extends horizontally.
Access one of the rafters then take the measurement this way.
The most precise way to find the roof s slope is by measuring it from the underside.
The standard pitch of most residential roofs ranges between 4 in 12 and 9 in 12.
Rafter rise run 1 5 6 2 25 36 38 25rafter 38 25 6 18 m.
Formula for calculating the slope the length of a slope is calculated using the pythagorean theorem.
Pitch rise run 1 5 6 25.
For example if your roof rises 7 inches for every 12 inches of horizontal run then your roof has a 7 in 12 pitch.
Angle arctan pitch arctan 0 25 14.
The slope of your roof is the ratio of the vertical distance or rise of the roof to the horizontal distance or run.
Finally you can find the roof pitch in the form of x 12.
Square root width x width height x height slope length.
Locate the level s 12 inch mark.