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Roof Pitch Calculator

Calculate your roof pitch from rise and run measurements. Get the pitch ratio (X:12), angle in degrees, and slope percentage β€” all in one click. Essential for roof framing, shingle selection, and estimating roofing materials.

πŸ“ The rise is how many inches the roof goes up for the given run (horizontal distance). Standard pitch is expressed as rise over a 12-inch run (e.g., 6:12 means 6 inches of rise per 12 inches of run).

πŸ“Š Roof Pitch Results

Pitch Ratioβ€”
Angle (Degrees)β€”
Slope Percentageβ€”
Roof Classificationβ€”
Rafter Multiplierβ€”

How to Use the Roof Pitch Calculator

Measure the rise (vertical height) and run (horizontal distance) of your roof in inches. You can measure these from inside the attic β€” the rise is the vertical height from the top of the wall plate to the ridge, and the run is the horizontal distance from the wall to the center of the ridge. Enter both values and click Calculate Roof Pitch. The calculator gives you the pitch ratio (standard format like 6:12), angle in degrees, slope percentage, roof classification, and the rafter length multiplier.

Common Roof Pitches & Their Uses

PitchAngleClassificationBest Use
Flat (0.25:12 to 1:12)1.2–4.8Β°FlatCommercial buildings; requires membrane roofing
Low Slope (2:12 to 4:12)9.5–18.4Β°Low SlopeModern homes, sheds; requires special underlayment
Conventional (4:12 to 9:12)18.4–36.9Β°ConventionalMost residential homes; standard asphalt shingles
Steep Slope (9:12 to 12:12)37–45Β°SteepA-frame homes, chalets; excellent snow shedding
Very Steep (12:12+)45Β°+Very SteepHistoric, Gothic, or specialty architecture

Understanding Roof Pitch Measurements

Why Roof Pitch Matters

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Frequently Asked Questions

You can measure from inside the attic. Measure 12 inches horizontally from the ridge along a rafter (or the ceiling joist). Then measure the vertical distance at that 12-inch mark from the rafter down to the joist (or from the joist up to the rafter, depending on what you're measuring against). That vertical measurement is your rise per 12 inches of run β€” your pitch. For example, if you measure 6 inches of rise over 12 inches of run, you have a 6:12 pitch.
The most common residential roof pitch is 6:12 (26.6Β°). Pitches between 4:12 and 9:12 work well for most homes, offering a good balance of aesthetics, attic space, material cost, and weather performance. In snowy regions, 8:12 or steeper is often recommended to help snow slide off rather than accumulate.
Standard asphalt shingles can be used on roofs with a pitch as low as 2:12, but they require special ice-and-water shield underlayment for the entire roof deck (not just the eaves). Below 2:12, asphalt shingles are not recommended β€” you'd need a membrane roofing system (like EPDM, TPO, or modified bitumen) designed for flat or near-flat roofs.
Steeper roofs cost more to roof because they have more surface area (for the same building footprint) and require more safety equipment and labor. A 12:12 roof has roughly 41% more surface area than a 6:12 roof. Additionally, roofers typically charge a "steep surcharge" (10–25% more) for pitches above 8:12 due to the increased difficulty and safety requirements.
In common usage they're interchangeable, but technically: pitch is expressed as a ratio with 12 as the denominator (e.g., 6:12), while slope is expressed as a percentage (e.g., 50%). Both describe the same thing β€” how steep the roof is. Pitch is standard in residential construction; slope percentage is more common in commercial flat roofing and civil engineering.