THE NUMBERS, EXPLAINED
How to use this calculator.
Applies to roof planes with one common pitch. Include overhangs in the horizontal projected area.
Start with your inputs
Enter horizontal projected roof area (m²), pitch (degrees). Keep amounts in the units shown on each field. The example is a starting point, not a recommended value.
| Input | Example value |
|---|---|
| Horizontal projected roof area (m²) | 100 |
| Pitch (degrees) | 30 |
A worked example
With the example inputs above, sloped roof area (m²) is 115.470054. Change the inputs to explore your own scenario.
Putting the example numbers into the formula
Sloped roof area (m²)
(100) ÷ cos((30) × π ÷ 180) = 115.470054
| Result | Example answer |
|---|---|
| Sloped roof area (m²) | 115.470054 |
How this is calculated
Sloped roof area (m²)
a ÷ cos(b × π ÷ 180)
Symbols and units
- a
- Horizontal projected roof area (m²)
- b
- Pitch (degrees)
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
cos uses an angle in radians. Convert degrees by multiplying by π/180.
π is the circle constant, approximately 3.141592653589793.
Assumptions and limits
Applies to roof planes with one common pitch. Include overhangs in the horizontal projected area.
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?
Sloped roof area (m²). 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: Applies to roof planes with one common pitch. Include overhangs in the horizontal projected area.
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.
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