Slope / grade calculator (ramp, roof, grade)

Calculate slope as a percentage, the angle and the ratio from rise and run.

Slope

8.33%

Angle4.76°

Ratio1 : 12

Slope % = rise ÷ run × 100. Use the same unit in both fields.

How the calculation works

Slope as a percentage is rise ÷ run × 100. The angle is the arctangent of that ratio. An accessible ramp, for example, is usually at most 8.33% (1:12).

Frequently asked questions

What is the max accessible ramp slope?

Generally 8.33% (a 1:12 ratio), per accessibility codes.

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Updated on June 18, 2026 · by Rafael Rossi · Methodology & sources