Wheelchair ramp calculator (ADA 1:12)
This wheelchair ramp calculator works out how long a ramp has to be for a given rise. Under the 2010 ADA Standards a ramp may be no steeper than 1:12 – one inch of rise needs 12 inches of run – and one run may rise at most 30 inches. A 24-inch rise therefore needs a 24 ft ramp.
Example: Rule: USA – ADA Standards · Units: inches and feet · Total rise 24 → Minimum ramp length: 24.0 ft (288 in) at 1:12 (8.33 %). Source: U.S. Access Board – 2010 ADA Standards for Accessible Design, 405 Ramps (405.2 slope 1:12, 405.6 rise 30 in, 405.7 landings 60 in, 405.8 handrails; read 09.10.2026). Updated: .
How it is calculated
Ramp length = rise × 12. The ADA Standards (405.2) allow a running slope of at most 1:12, which is 8.33 %. Every inch of rise needs one foot of horizontal run. Slopes up to 1:20 count as walking surfaces, not ramps.
ADA ramp length chart
| Rise | Ramp length (1:12) | Runs |
|---|---|---|
| 6 in | 6 ft | 1 |
| 12 in | 12 ft | 1 |
| 24 in | 24 ft | 1 |
| 30 in | 30 ft | 1 |
| 36 in | 36 ft + one 5 ft landing = 41 ft | 2 |
A run may rise at most 30 inches (405.6). Above that you need an intermediate landing, at least 60 inches (5 ft) long (405.7.3). Every run also needs a level landing at the top and the bottom; those are not part of the ramp length shown. Ramps rising more than 6 inches need handrails on both sides (405.8), and the clear width must be at least 36 inches (405.5). In existing buildings Table 405.2 allows steeper slopes for very small rises where space is limited – the calculator always uses 1:12.
Examples
- Two steps, 14 in: 14 ft of ramp.
- Porch 30 in high: 30 ft – the longest single run the ADA allows.
- Door 36 in above grade: two runs of 18 ft with a 5 ft landing: 41 ft in total.
- In metric: 60 cm rise needs 7.20 m.
The slope calculator turns rise and run into percent and degrees; for steps instead of a ramp see the stair calculator.
Other countries
Choose the rule: Spain (CTE DB SUA) allows 10 % for accessible runs under 3 m, 8 % under 6 m and otherwise 6 %. Türkiye’s zoning regulation sets 1:12 up to 15 cm and 1:20 above 100 cm. Japan’s barrier-free ordinance allows 1/12, or 1/8 up to 16 cm of rise.
Frequently asked questions
How long does a wheelchair ramp need to be?
Under the ADA 1:12 rule, one foot of ramp per inch of rise: 24 in of rise needs 24 ft, 30 in needs 30 ft.
What is the ADA ramp slope?
At most 1:12 (8.33 %) for new construction. Up to 1:20 the surface is a walkway, not a ramp.
When does a ramp need a landing?
Every run may rise at most 30 inches. Above that you need an intermediate landing at least 60 inches long – and level landings at the top and bottom of every run.
Does a ramp need handrails?
Under the ADA, yes when the rise is more than 6 inches. A 6-inch rise with a 6 ft ramp does not need them.
How wide must an ADA ramp be?
At least 36 inches clear width between handrails (405.5).
Can I check an existing ramp?
Yes – enter its horizontal length. A 36 in rise over 30 ft is 1:10 (10 %), steeper than 1:12.
Sources and legal basis
As of: · Editorial policy
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