Step-by-step instructions
- Enter or select Horizontal run (ft).
- Enter or select Vertical rise (ft).
- Tap Calculate.
- Review the result shown directly below the calculator.
Rafter Length Calculator
Estimate common rafter length from run and rise.
How to use the Rafter Length Calculator
Estimate common rafter length from run and rise.
What the inputs mean
- Horizontal run (ft)
- Enter the value requested by this field label.
- Vertical rise (ft)
- Enter the value requested by this field label.
Formula or calculation method
The Pythagorean theorem is used: a² + b² = c².
Example
For example, sides of 3 and 4 produce a hypotenuse of 5.
How to understand the result
Use the result as an estimate based on the values you entered. For planning decisions, double-check that the input units and assumptions match your real situation.
Tip: Keep all values in compatible units and use values from the same time period when the calculator compares two amounts.