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Slope & Grade Calculator

Convert a rise and run measurement into slope percentage and angle in degrees.

Computed in your browser — nothing you enter is uploaded. Figures are presented in United States units and terminology, and each formula’s basis is cited under regulatory standards below.

Last verified 2026-08-25 · v1.0.0

Market
Imperial · sales tax
39 ft3.5 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Slope grade

8.974 %

High confidence
Angle
5.13 degrees

At the values currently entered, the slope grade works out to 8.97 %. Figures are shown in United States units and terminology; switch the market above if you are building elsewhere.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.

Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Regulatory standards & verification citations

  • Grade percent = (rise / run) x 100; angle in degrees = arctangent(rise / run)

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Frequently asked questions

What's a typical maximum slope for a wheelchair ramp?
The ADA requires a maximum running slope of 1:12 (about 8.33%, roughly 4.8°) for accessible ramps — this calculator's first example is exactly that ratio.
What slope do driveways typically need for drainage?
A minimum of about 1-2% grade is commonly recommended so water sheets off rather than pooling, while over 15-20% starts to become difficult to drive and park on safely, especially in icy conditions.
Is grade percent the same as degrees?
No — they're related but not linearly the same (a 100% grade is a 45° angle, not 90°). This calculator gives you both so you can use whichever unit your project's spec calls for.