Roof Pitch Calculator

The roof pitch calculator tools below will help you calculate the slope from every possible angle. Each tool below performs a specific operation that involves measuring and calculating the slope. Using our Roofing Pitch Calculator(s) below, you can calculate roof slope, area, rafter length and other dimensions, and convert Pitch to Degrees.

1) Calculate Roof Slope based on Rafters Length:

Roof Span: ft. in.
Roof Rise: ft. in.
Pitch = / 12″

2) Convert Roof Pitch to Angle (Degrees) – enter pitch in the first box – calculation is automatic.

Enter Pitch: / 12″
Results: degrees angle


Using the diagram below, measure your roof from the ground, and enter dimensions into the calculator #2 above. Enter roof span (also known as gable side width), and the rise above base line.

To calculate the slope and size, measure your roof and plug in your measurements in accordance with the diagram below. Enter EITHER Roof Rise or Pitch.

Roof Measuring Diagram - www.RoofCalc.org

Measuring roof rise:

If you do not know the rise, and do not have a ladder or cannot access your roof in order to measure it, you can accurately estimate the rise by measuring 3 spans of siding (typical vinyl siding has 4″ exposure, so 3 spans would be equal to 12″ or 1 foot), and calculating the number of spans from base line to the peak. Since most homes have a Rake wood, which is usually 6-8″ wide, you can add that width to the rise.



Example: If you have 19 spans of siding at 4″ exposure (width) of each span, and a 6″ rake board, the the Rise would be:

[6" + (19 * 4")] / 3 = 6′ 10″ roof rise.

measuring roof slope diagram


Converting roof pitch (US / Canadian slope measuring method) to degrees (European slope measuring method) can be useful in figuring out the roof geometry, or for roofers from Europe who are not accustomed to US system. See Table below:

roof pitch and degrees table





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5 thoughts on “Roof Pitch Calculator

    • Pa,

      Quick answer – because it is not a straight line increase of 3.75 degrees, for each 1/12″. I will look into why you are getting “NaN”

    • PA,

      If we use that logic, then 24 pitch roof should be 90 degrees, right (12*2 same as 45 degrees * 2)? But it’s not. It’s about 63.5 degrees. Like I said – it is not a straight line. Each step is smaller than the previous one. Look at last diagram:

      Roof pitch to degrees conversion table

      1 pitch is 4 degrees.
      2 pitch is 9.5 degrees – that’s a 5.5 degrees step.
      3 pitch is is 14 degrees – that is a 4.5 degrees step.

      from there it slowly declines or stays the same…

      However, those are not exact numbers – it’s more like 14.04 degrees for a 3 pitch.

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