MasterTool

Ramp Calculator

Find ramp run, length, slope and angle for any rise, with the ADA 1:12 maximum-slope check.

Loading calculator…

What this tool does

Find ramp run, length, slope and angle for any rise, with the ADA 1:12 maximum-slope check. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.

How to use the Ramp Calculator

  1. Enter or select total rise in in.
  2. Enter or select run per 12 of rise (12 = ada 1:12).
  3. Read the calculated result; change any measurement to compare alternatives.

Formula

run = rise × ratio (ratio = the 12 in 1:12); slope % = 100 / ratio; ramp length = √(rise² + run²); angle = atan(rise/run)
rise
Total rise (in, before metric conversion)
ratio
Run per 12 of rise (12 = ADA 1:12)

ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.

Worked example

For ramp calculator, the following measurements illustrate the exact method: Total rise: 30; Run per 12 of rise (12 = ADA 1:12): 12.

Inputs

  • Total rise30 in
  • Run per 12 of rise (12 = ADA 1:12)12

Result

  • Required run360 in
  • Required run (feet)30 ft
  • Ramp surface length361.25 in
  • Slope (%)8.33
  • Ramp angle (degrees)4.76
  • ADA 1:12 checkMeets the ADA maximum slope of 1:12

Results explained

Required run
Required run from the formula above, expressed in in before metric conversion. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.
Required run (feet)
Required run (feet) from the formula above, expressed in ft before metric conversion. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.
Ramp surface length
Ramp surface length from the formula above, expressed in in before metric conversion. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.
Slope (%)
Slope (%) from the formula above. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.
Ramp angle (degrees)
Ramp angle (degrees) from the formula above. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.
ADA 1:12 check
ADA 1:12 check from the formula above. ADA Standards limit new ramp slopes to 1:12 (8.33%) with a maximum rise of 30 in per run. Residential and landscape ramps may follow other rules — verify local code.

Frequently asked questions

At the ADA maximum slope of 1:12, run = 30 × 12 = 360 in = 30 ft of run, plus level landings at top and bottom.

1:12 — one unit of rise per twelve units of run (8.33%, about 4.8°). It is a maximum steepness, not a target; 1:16 or 1:20 is noticeably easier to use.

atan(1/12) ≈ 4.76 degrees. Small angle, long ramp — that is the point of the standard.

ADA runs may rise at most 30 in before a level landing (at least 60 in long). A 36 in rise therefore needs two runs with a landing between.

Private homes are usually not bound by the ADA, and steeper ramps exist — but anyone self-propelling a wheelchair will struggle past about 1:10. Build as gentle as your space allows.