How to Measure Roof Pitch (4 Easy Methods + Chart)
Short answer: roof pitch is how many inches the roof rises for every 12 inches it runs horizontally. To measure it, hold a level horizontally against a rafter (or the roof), mark 12 inches along the level, then measure straight up or down from that mark to the rafter. If that distance is 6 inches, the roof is a 6/12 pitch (about 26.6°).
Already have two measurements? Enter them in the roof pitch calculator to get the pitch, the angle and the roof area.
What you need
- A level, 24 inches or longer (a 12 inch level works if you mark it carefully)
- A tape measure
- A pencil, or a piece of tape to mark 12 inches on the level
Method 1: from the attic (safest)
Rafters run parallel to the roof surface, so measuring a rafter gives you the roof’s pitch without going up on the roof.
- Mark 12 inches from one end of your level.
- Hold that end of the level against the underside of a rafter and make the level perfectly horizontal (bubble centered).
- At the 12 inch mark, measure straight up from the level to the underside of the rafter.
- That number is the rise: a rise of 6 inches means 6/12.
Method 2: at a gable end or rafter tail, from a ladder
On many houses the sloped trim board at the gable end, or the exposed rafter ends under the eaves, follow the roof’s slope. Use the same level-and-tape method against that edge. Keep the ladder secure, and don’t lean out.
Method 3: any two measurements
You don’t have to use exactly 12 inches. Measure any horizontal distance (the run) and the vertical drop over it (the rise), then:
Pitch = rise ÷ run × 12. For example, a drop of 5 inches over 9½ inches is 5 ÷ 9.5 × 12 = 6.32/12, a little over 6/12 (27.8°).
Method 4: a phone or digital angle finder
Angle apps and digital levels give you degrees. Lay the phone on a rafter or the roof surface and read the angle, then use the table below to turn degrees into pitch. A reading of about 26.6° is a 6/12 roof.
Roof pitch to degrees chart
| Pitch | Angle | Percent slope | Roof area multiplier |
|---|---|---|---|
| 1/12 | 4.8° | 8.3% | 1.003 |
| 2/12 | 9.5° | 16.7% | 1.014 |
| 3/12 | 14.0° | 25% | 1.031 |
| 4/12 | 18.4° | 33.3% | 1.054 |
| 5/12 | 22.6° | 41.7% | 1.083 |
| 6/12 | 26.6° | 50% | 1.118 |
| 7/12 | 30.3° | 58.3% | 1.158 |
| 8/12 | 33.7° | 66.7% | 1.202 |
| 9/12 | 36.9° | 75% | 1.250 |
| 10/12 | 39.8° | 83.3% | 1.302 |
| 12/12 | 45.0° | 100% | 1.414 |
The multiplier turns the flat area under the roof (the house footprint plus overhangs) into the actual sloped roof area. A 1,500 sq ft footprint under a 6/12 roof is 1,500 × 1.118 = about 1,677 sq ft of roof. The roofing calculator does this and turns the result into shingle bundles.
What your pitch means for roofing
| Roofing | Minimum pitch (2021 IRC) | Section |
|---|---|---|
| Asphalt shingles | 2/12; between 2/12 and 4/12 they need a double layer of underlayment | R905.2.2 |
| Clay and concrete tile | 2½/12 | R905.3.2 |
| Metal roof shingles | 3/12 | R905.4.2 |
Below 2/12, asphalt shingles aren’t allowed, and a low-slope roofing system is used instead. Your local code and the shingle maker’s instructions have the final say.
Safety
- Measure from the attic or a ladder whenever you can. You don’t need to stand on the roof to find its pitch.
- Stay off wet, icy, mossy or steep roofs. If you must go up, use proper fall protection, or hire a roofer.
Common questions
Is a 4/12 roof pitch steep?
No. 4/12 is about 18.4°, a fairly low slope. It’s at the top of the 2/12 to 4/12 range where asphalt shingles need double underlayment under the 2021 IRC.
What is a 6/12 roof pitch in degrees?
About 26.6°.
Can I measure roof pitch from the ground?
Only roughly, by photographing the gable end straight on and measuring the angle in a photo app. For an accurate number, measure a rafter from the attic.
What’s the difference between pitch and slope?
People use them interchangeably. Pitch is usually written as rise in 12 (6/12); slope may be written as a percentage (50%) or an angle (26.6°). They all describe the same steepness.
Sources
- International Code Council: 2021 IRC chapter 9 (roof assemblies): R905.2.2 asphalt shingles, R905.3.2 clay and concrete tile, R905.4.2 metal roof shingles.
- GAF Timberline HDZ data sheet: minimum slope 2:12 for architectural shingles.