Roof Pitch Calculator

Convert rise and run into roof pitch (x/12), angle in degrees, slope percentage and the pitch multiplier used to turn a flat footprint into true roof area.

Roof pitch

6/12

  • Angle26.6 °
  • Slope50 %
  • Pitch multiplier (rafter factor)1.118

Estimates only. Round up when you order, and confirm structural details with your local building code.

How to use it

  1. Measure the rise over a known run — a 12 in level and a tape on the roof or rafter works.
  2. Enter rise and run.

The formula

Pitch = rise ÷ run × 12 (written as x/12)

Angle = arctan(rise ÷ run)

Multiplier = √(1 + (pitch ÷ 12)²)

Worked example

Rise6 in
Run12 in

Result

Roof pitch6/12
Angle26.6 °
Slope50 %
Pitch multiplier (rafter factor)1.118

Tips before you order

  • Pitches below 4/12 need special underlayment for asphalt shingles; below 2/12, shingles aren't allowed.
  • Walk-able roofs are usually 6/12 or lower.

Questions

What angle is a 6/12 pitch?

26.6 degrees.

What angle is a 4/12 pitch?

18.4 degrees.