Convert Every Roof Pitch Format
Solve from rise and run, angle, percentage slope, pitch ratio, or rafter length and run. All other representations update from the same right-triangle geometry.
Roof Pitch Formulas
Angle = arctangent(rise ÷ run). Percentage slope = rise ÷ run × 100. Rafter length = √(rise² + run²), and slope factor = rafter length ÷ run.
Understanding Pitch Ratios
A ratio such as 6:12 describes vertical rise over 12 horizontal units. Because it is dimensionless, the same ratio applies in inches, feet, millimetres or metres.
Geometry Is Not Structural Design
Pitch affects geometry but does not prove that rafters, connections, sheathing or roof coverings are suitable. Structural and weatherproofing requirements must be checked separately.
Roof Pitch Calculator FAQ
How do I calculate roof pitch?
Divide rise by horizontal run. Multiply by 100 for percentage slope, use arctangent for degrees, or scale the ratio to a 12-unit run.
What does a 6:12 roof pitch mean?
The roof rises 6 units for every 12 horizontal units of run. It is approximately 26.57 degrees or a 50% slope.
What is the difference between run and rafter length?
Run is horizontal distance. Rafter length is the sloping hypotenuse and equals the square root of rise squared plus run squared.
Can I enter an angle instead of rise?
Yes. Choose Angle + run and enter both values. The calculator derives rise, percentage, ratio and rafter length.
Does the calculator work in metric?
Yes. Rise, run and rafter length can use any consistent metric or imperial unit.
Does roof pitch prove the roof is structurally adequate?
No. The calculator converts geometry only and does not check member strength, covering limits, drainage, wind or snow loads.