Ramp slope and length calculator
An accessible ramp is set out from the rise and the maximum gradient the code allows. 1:12 (8.33%) is the common ceiling; gentler gradients allow longer runs between landings. Enter the rise you need to overcome and the gradient to see the run, sloped length and how many landings are required.
ramp slope calculator
- Horizontal run
- 7,200mm
- Sloped ramp length
- 7,225mm
- Gradient
- 8.33% (4.76°)
- Intermediate landings
- 1 — meets the usual 1:12 accessible limit
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Formula
run = rise × ratio · length = √(run² + rise²) · gradient % = 100 ÷ ratio1:12 is 8.33%, 1:15 is 6.67%, 1:20 is 5%. Rises above roughly 500 mm on a 1:12 ramp need an intermediate landing; check the governing code for the exact figure.
Worked examples
| Input | Result |
|---|---|
| 600 mm rise at 1:12 | 7200 mm run, one intermediate landing |
| 600 mm rise at 1:20 | 12,000 mm run, no landing required |
| 150 mm threshold at 1:12 | 1800 mm run |
Questions
What is the maximum slope for a wheelchair ramp?
1:12 (8.33%) is the widely used maximum for new accessible routes, with gentler gradients preferred on long runs. Existing-building alterations sometimes permit steeper short ramps — always cite the governing code on the drawing.
Does the run include landings?
No. The figure above is the sloped section only. Add 1500 mm minimum for each intermediate landing and for the level areas at the top and bottom.
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