Free · Roofing & slopes

Ramp Rise, Run & Slope Calculator

Calculate ramp geometry from a selected ratio or your own rise and run.

  • Formula & worked example
  • Private in your browser
  • No signup
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Calculator inputs

Enter the values you know

Results update as you type. Edit a result to calculate another value, or lock a value to keep it fixed.

Ramp specifications
Calculated: 12
Ramp details
%
Result

Your calculation

Rise-to-run ratio
12

How to use this calculator

  1. Enter the values you know in the units shown. Leave unknown values blank.
  2. Results update automatically as you type. Edit a result to calculate another value, or lock a value to keep it fixed.
  3. Reset restores the starting fields. A worked example appears below.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A rise-to-run ratio of 1:12 requires twelve units of horizontal run for each unit of rise. Geometry alone does not establish accessibility compliance; landings, width, surface and local requirements also matter.

Gradient (%) = 100 × rise / run; surface length = √(rise² + run²)

Worked example

Enter these known values and leave the other values blank.

Application
Unassisted user, ADA max slope (1:12)
Ramp type
Straight
Rise
30 cm
Rise-to-run ratio
12
Slope angle
4.76 deg
Elevation grade
8.33 %
Run
3.6 m
Ramp length
3.6125 m

Assumptions and limitations

  • Inputs must satisfy the validation rules. Editing a result can recalculate an earlier input; lock values you want to keep fixed.

Common questions

What does this ramp slope calculation tell me?

A rise-to-run ratio of 1:12 requires twelve units of horizontal run for each unit of rise. Geometry alone does not establish accessibility compliance; landings, width, surface and local requirements also matter.

Can I calculate a different unknown?

Yes. Clear that field and enter the other known values. The calculator uses the available inverse equations.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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