What roof pitch means
Roof pitch is how many inches a roof rises for every 12 inches it runs horizontally. A 6/12 roof climbs 6 inches for each foot of run. It's the standard way roofers, framers and shingle makers describe how steep a roof is.
The calculator turns rise and run into three other useful numbers: the angle in degrees, the slope as a percentage, and the multiplier you use to turn a flat footprint into true roof area.
| Pitch | Angle | Area multiplier |
|---|---|---|
| 3/12 | 14.0° | 1.031 |
| 4/12 | 18.4° | 1.054 |
| 6/12 | 26.6° | 1.118 |
| 8/12 | 33.7° | 1.202 |
| 12/12 | 45.0° | 1.414 |
How to measure rise and run
The safest way is from inside the attic. Hold a level against the bottom of a rafter, mark 12 inches along the level, and measure straight up from that mark to the rafter. That number is your rise. You can also measure from a gable end with a level and tape, or use a pitch gauge app from the ground.
If you can't measure 12 inches, measure any run and rise. The calculator scales it to 12 for you.
Why pitch matters
- Materials: most asphalt shingles need at least a 2/12 pitch, with extra underlayment on low slopes. Steeper roofs suit tile and slate.
- Area: a steeper roof has more surface, so it needs more shingles. Plug your pitch into the roofing calculator.
- Safety: roofs steeper than about 6/12 are hard to walk on. Use fall protection or hire a pro.
Frequently asked questions
How do I calculate roof pitch?
Measure how many inches the roof rises over 12 inches of horizontal run. A rise of 6 inches over 12 inches is a 6/12 pitch.
What angle is a 6/12 roof pitch?
About 26.6 degrees.
What is the most common roof pitch?
Pitches between 4/12 and 9/12 are the most common on houses in the U.S.
How do I convert roof pitch to degrees?
Take the arctangent of rise divided by run. For a 4/12 roof, arctan of 4/12 is about 18.4 degrees. The calculator does it for you.
Results are estimates for planning. Product coverage, site conditions and installation methods vary, so check manufacturer guidance before you buy.