Mobility & Home Access
Wheelchair Ramp Slope Calculator
Use this wheelchair ramp slope calculator to turn a step or threshold height into the ramp length you need. It works as an ADA ramp slope calculator, a handicap ramp length calculator, and a ramp incline, gradient, and percent-grade calculator — all from a single rise measurement.
Ramp needed
Ramp results
A 24 in rise at 1:12 needs about 24 ft of ramp run plus level landings at the top and bottom.
Reference: ADA
Japan wheelchair ramp guidance
Japan's MLIT barrier-free design guidance uses a slope of 1:12 or gentler as a principal reference and describes 1:15 or gentler as desirable outdoors where rain must be considered. A 1:20 slope is gentler again. Select the Japan profile above to make the metric result and Japanese reference explicit.
Official source: MLIT, Barrier-Free Building Design Standard (FY2025 revision). The calculator estimates the sloped run only. Landings, handrails, width, drainage and residential requirements must be checked for the actual site.
How the ramp slope is calculated
A ramp's slope is the ratio between how high it climbs (the rise) and how far it travels horizontally (the run). This calculator starts from the rise you measure and the slope ratio you choose:
ramp length (run) = rise × ratio
From there it derives the rest: the percent grade is rise ÷ run × 100, and the incline angle is arctan(rise ÷ run) in degrees. At the ADA maximum of 1:12, that is always an 8.33% grade and about a 4.76° angle, no matter the rise.
ADA wheelchair ramp slope guide
| Slope ratio | Percent grade | Angle | When it is used |
|---|---|---|---|
| 1:20 | 5.0% | 2.86° | Gentlest. Below this, it is technically a sloped walk and may not need handrails. |
| 1:16 | 6.25% | 3.58° | Easier to self-propel; good when space allows. |
| 1:12 | 8.33% | 4.76° | ADA maximum for a new public ramp. The common target. |
| 1:10 | 10.0% | 5.71° | Occupied or assisted use only; too steep to self-propel safely. |
| 1:8 | 12.5% | 7.13° | Short threshold transfers with help only; not for independent use. |
Landings and rise limits
ADA ramps need a level landing at least 60 inches (about 1.5 m) long at the top and bottom, and an intermediate landing for every 30 inches (about 760 mm) of vertical rise. This calculator counts those landings for you. Long ramps often switch back to fit the available yard space, and each turn needs its own landing.
Common mistakes
- Measuring only the last step instead of the full height from the ground to the door threshold.
- Using a steep 1:8 portable ramp for daily independent use — fine for loading a folded chair, unsafe to wheel up alone.
- Forgetting that landings and turns add length and space beyond the sloped run.
- Ignoring handrails: ADA ramps with a rise over 6 inches generally need handrails on both sides.
Safety note
These figures follow widely cited ADA accessibility guidance and are a planning starting point. Residential building codes, frost depth, drainage, and handrail rules vary by location. Confirm requirements locally and have a licensed contractor verify any permanent ramp.
FAQ
Wheelchair ramp slope FAQ
What is the ADA wheelchair ramp slope?
The ADA maximum slope for a new wheelchair ramp is 1:12 — about 4.8 degrees or an 8.33 percent grade. One unit of rise needs at least 12 units of ramp length.
How long does a wheelchair ramp need to be?
At 1:12, ramp length equals the rise times 12. A 24 inch rise needs about 24 feet of ramp run, plus level landings at the top and bottom.
How do I calculate ramp slope from rise and run?
Slope ratio is run ÷ rise, percent grade is rise ÷ run × 100, and the incline angle is arctan(rise ÷ run). Enter the rise and pick a ratio and the calculator does the rest.
When does a ramp need a landing?
Provide a level landing at the top and bottom, plus an intermediate landing for every 30 inches of rise. Landings should be at least 60 inches long.
Can I use a slope steeper than 1:12?
Steeper slopes like 1:8 or 1:10 are only for short, assisted, or occupied transfers. For independent daily use, stay at 1:12 or gentler and confirm local code.