Free Tool
Roof Pitch Calculator
Enter rise and run to get your roof's pitch as a ratio and in degrees.
Already know your pitch as X/12? Enter your X as rise and 12 as run. Any consistent unit works for both fields — it’s the ratio that matters, not the unit.
Pitch
6/12
Angle
26.6°
Grade
50%
Roof area multiplier
1.118
“Roof area multiplier” is how much bigger your actual roof surface is than its flat footprint at this pitch — see the Roof Squares & Shingle Calculator to turn that into a material estimate.
What is roof pitch?
Roof pitch is how steep a roof is, expressed as inches of vertical rise for every 12 inches of horizontal run. A “6/12” roof rises 6 inches for every 12 inches you move horizontally — the higher the first number, the steeper the roof.
How to measure your roof’s rise and run
From the attic, or on the roof itself with a level: hold a level horizontal against a rafter or the roof surface, measure exactly 12 inches out along the level, then measure straight down from that point to the roof surface. That vertical distance, in inches, is your rise over a 12-inch run.
Pitch vs. angle vs. percent
These are the same slope described three different ways, for three different audiences. Pitch (X/12) is what roofers use on a daily basis — it matches how rafters are actually laid out and cut. Angle in degrees is what a digital angle finder or smartphone level app reads directly off the roof surface. Percent grade (rise divided by run, as a percentage) shows up more in civil engineering and drainage contexts than in roofing itself, but occasionally appears on plans or permit documents.
Pitch reference table
Common pitches with their angle, grade, and roof area multiplier — cross-checked against independently published roofing references.
| Pitch | Angle | Grade | Area multiplier |
|---|---|---|---|
| 1/12 | 4.8° | 8% | 1.003 |
| 2/12 | 9.5° | 17% | 1.014 |
| 3/12 | 14.0° | 25% | 1.031 |
| 4/12 | 18.4° | 33% | 1.054 |
| 5/12 | 22.6° | 42% | 1.083 |
| 6/12 | 26.6° | 50% | 1.118 |
| 7/12 | 30.3° | 58% | 1.158 |
| 8/12 | 33.7° | 67% | 1.202 |
| 9/12 | 36.9° | 75% | 1.250 |
| 10/12 | 39.8° | 83% | 1.302 |
| 11/12 | 42.5° | 92% | 1.357 |
| 12/12 | 45.0° | 100% | 1.414 |
Worked example
A roof measures 8 inches of rise over a 12-inch run:
- 1. Pitch: 8/12
- 2. Angle: arctan(8/12) ≈ 33.7°
- 3. Grade: (8/12) × 100 ≈ 67%
- 4. Roof area multiplier: √(8² + 12²) / 12 ≈ 1.202 — about 20% more surface area than the flat footprint
Frequently asked questions
What is roof pitch?
How steep a roof is, expressed as inches of vertical rise for every 12 inches of horizontal run — a "6/12" roof rises 6 inches for every 12 inches you move horizontally. It's the standard way U.S. roofers describe slope.
What's the difference between pitch, angle, and percent?
They're the same slope described three ways. Pitch (X/12) is what roofers use day to day. Angle in degrees is what a digital angle finder or level app reads. Percent grade is rise divided by run as a percentage — more common in civil/drainage contexts than roofing.
How do I measure my roof's rise and run without going on the roof?
From the attic: hold a level horizontal against a rafter, measure exactly 12 inches out from the ridge along the level, then measure straight down from that point to the rafter. That vertical measurement is your rise.
What roof pitch is considered steep?
OSHA defines any roof steeper than 4/12 as a "steep roof" for job-site safety purposes — above that threshold, warning-line systems aren't permitted, and the crew needs guardrails, safety nets, or a personal fall-arrest system instead.
Does a steeper pitch mean more roofing material?
Yes. A steeper pitch means more actual roof surface for the same building footprint — a 12/12 pitch has about 41% more surface area than a flat footprint of the same size, versus about 12% more for a 6/12 pitch.