Enter Rise and Run — Angle will be calculated. For roof pitch, set Run to 12.
Enter values as decimals (e.g. 6.5, not 6 1/2). Converting a feet-and-inches measurement? Use the converter.
Pitch equivalent
—
Grade equivalent
—%
angle = atan(rise ÷ run)
True to scale from about 2° to 85°. Numbers are always exact.
Reference tables
Pitch
Degrees
Percent grade
Material minimums: below 2/12 needs low-slope/membrane roofing (not shingles). 2/12–4/12 asphalt shingles need special underlayment. 4/12 and up is standard shingle installation.
Rough guides for comfortable, code-friendly residential stairs. R = riser height, T = tread depth:
Rule
Formula
Example
Classic ratio
R ≈ 7″, T ≈ 11″
7″ rise, 11″ run
Sum rule
R + T = 17–18″
7 + 11 = 18″
Stride rule
2R + T = 24–25″
2(7) + 11 = 25″
Deeper treads want a shallower riser to keep stride length consistent, and vice versa. Codes vary, but riser ≤ 7¾″ and tread ≥ 10″ is a common baseline — check your local code before building.
Common slope ratios for ramps, expressed as rise:run:
Use case
Slope
Angle
ADA comfortable
1:16–1:20
2.9–3.6°
ADA max (public)
1:12
4.8°
Residential, wheel-friendly
1:8–1:6
7.1–9.5°
Residential, walk-only
1:6–1:4
9.5–14.0°
ADA ramps also require a level landing at least every 30″ of rise, and handrails once rise exceeds 6″. Residential ramps (a shed or deck, say) aren't held to ADA slope, and are often built steeper than this table — up to 2:12 or even 3:12 — when the priority is a short footprint over walk-only traffic. But comfort for wheeling anything (a hand truck, a wheelchair, a stroller) drops off fast past about 1:8, so if a cart's involved, stay closer to the range above. Always confirm against your local code — these are general guidelines, not a substitute for it.
Drainage is usually specified in inches per foot or percent rather than a rise:run ratio — same underlying slope, just much shallower:
Use case
Slope
Angle
Patio/deck, away from house
1/4″ per ft (≈2%)
1.2°
Gutters, toward downspout
1/16–1/4″ per ft
0.3–1.2°
French drain / perimeter pipe
1% min, 2% ideal
0.6–1.2°
Too flat and water pools instead of draining; too steep next to a foundation risks erosion or, in freeze climates, ice buildup. These are starting points — confirm against your local code, especially for anything tied to a foundation.
Feet-Inches Converter
Convert a feet-and-inches reading into the decimal value this calculator uses, without doing the fraction math by hand.