THE NUMBERS, EXPLAINED
How to use this calculator.
Use the same units for rise and run. Run is horizontal, not the roof slope length.
Start with your inputs
Enter rise, horizontal run. Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Rise | 3 |
| Horizontal run | 4 |
A worked example
With the example inputs above, pitch (degrees) is 36.869898. Change the inputs to explore your own scenario.
Putting the example numbers into the formula
Pitch (degrees)
atan((3) ÷ (4)) × 180 ÷ π = 36.869898
Slope ratio
(3) ÷ (4) = 0.75
| Result | Example answer |
|---|---|
| Pitch (degrees) | 36.869898 |
| Slope ratio | 0.75 |
How this is calculated
Pitch (degrees)
atan(a ÷ b) × 180 ÷ π
Slope ratio
a ÷ b
Symbols and units
- a
- Rise
- b
- Horizontal run
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Calculation steps and notation
atan returns the inverse tangent in radians. Multiply by 180/π for degrees.
π is the circle constant, approximately 3.141592653589793.
Assumptions and limits
Use the same units for rise and run. Run is horizontal, not the roof slope length.
Calculations use the values you enter. Blank or invalid inputs show an error instead of silently substituting zero. Results are displayed to useful precision; calculations retain the underlying numeric precision.
Questions about this tool
What does the result tell me?
Pitch (degrees); Slope ratio. The result applies to the method and inputs described above. Check the units and assumptions before using it in a decision.
Why might another calculator differ?
Differences in units, rounding, timing or model definitions can produce different answers. Compare the input definitions and the method, rather than only the final number. For this tool: Use the same units for rise and run. Run is horizontal, not the roof slope length.
Are my inputs stored or sent to AI?
Calculations on this page happen in your browser. The separate AI question finder sends its submitted conversation to OpenAI; these calculator fields are not sent. Favourites and recent tool names are stored locally. A shared link contains the inputs you choose to include.
Review status
Software example and browser checks are recorded in our quality report. No external expert review is claimed. Created with coding assistance; calculations run as ordinary browser code.
Read the quality report →