Ramp length = rise × N for a 1:N slope. Under the US ADA (1:12, max 30 in rise per run), a 24 in rise needs a 24 ft ramp. Under UK Part M at 1:15 (max 5 m going per flight), a 600 mm rise needs two 4.5 m flights and a 1.5 m landing (10.5 m in total).
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Total ramp length (with landings)
10.50m
Gradient
1:15 (6.67%, 3.81°)
Flights
2
Length of each flight
4.50 m rising 300 mm
Intermediate landings
1 × 1.50 m
Sloped surface length
9.02 m
Add level landings at the top and bottom, handrails, edge protection and the clear width your code requires. Check the current edition of the standard.
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Flights = ⌈600 mm ÷ 333 mm max per flight⌉ = 2; each rises 300 mm
Flight length = rise × 15 = 4.50 m
Total = 2 × 4.50 m + 1 × 1.50 m landing = 10.50 m
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Generated with myconstructioncalculator.com. Estimates for planning and ordering only; verify against drawings and specifications.
Formulas
Flights = ⌈total rise ÷ max rise per flight⌉Flight length = rise per flight × NTotal length = flights × flight length + (flights − 1) × landing
Worked examples
UK Part M, 1:15, 600 mm rise: max rise per flight = 5 m ÷ 15 = 333 mm → 2 flights of 300 mm rise, each 4.5 m long, plus a 1.5 m landing = 10.5 m.
US ADA, 1:12, 24 in rise: one run (under 30 in) of 24 × 12 = 288 in = 24 ft.
Ramp length for a rise (no landings)
Rise
1:12
1:15
1:20
150 mm
1.8 m
2.25 m
3.0 m
300 mm
3.6 m
4.5 m
6.0 m
450 mm
5.4 m
6.75 m
9.0 m
600 mm
7.2 m
9.0 m
12.0 m
12 in
12 ft
15 ft
20 ft
24 in
24 ft
30 ft
40 ft
Frequently Asked Questions
What is the ADA ramp slope?
A maximum of 1:12 (8.33%), which is 1 in of rise for every 12 in of run, with no single run rising more than 30 in and level landings at least 60 in long.
How long does a ramp need to be?
Multiply the rise by the slope ratio. At 1:12 a 24 in rise needs 24 ft; at 1:20, 40 ft. Add landings between runs and at the top and bottom.
What are UK Part M ramp gradients?
Up to 1:12 for flights of up to 2 m going, 1:15 up to 5 m, and 1:20 up to 10 m, with landings between flights.
References
2010 ADA Standards §405: ramps: max slope 1:12, max rise 30 in per run, landings 60 in long
UK Approved Document M: ramp gradients 1:12 (≤ 2 m going), 1:15 (≤ 5 m), 1:20 (≤ 10 m)
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