Ramp slope calculator: ADA ramps, car park ramps and parking layout
Enter a rise to get the ramp length, runs, landings and slope for an ADA wheelchair ramp or a car park ramp with transitions, or lay out a parking module with stall, aisle and accessible space counts. Pair it with our stair calculator for the steps beside the ramp.
2010 ADA §405 rampsCar park ramp transitionsParking module at 90°, 60°, 45°, 30°ADA accessible stall countMetric or imperial
Calculator
Accessible pedestrian ramp
Slope 1:12 maximum, 30" (760 mm) rise per run, 60" (1525 mm) landings, 36" (915 mm) clear width, handrails where a run rises more than 6" (150 mm).
Type 1:15, 6.67% or 3.81°.
Empty means one continuous run.
In the direction of travel.
Finished level at the bottom to finished level at the top.
Checks the 36" (915 mm) minimum.
Car park ramp
Level to level the ramp connects.
Type 15%, 1:6 or 8.5°.
Transitions are then needed even on a 1:10 ramp (IStructE §4.3.7).
Parking layout
Length of the bay along the aisle.
Empty uses the typical width.
For the ADA accessible space count. Empty uses the stalls in this module.
Your ramp
Required run length
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ADA 2010 checks
What the ramp also needs
Your car park ramp
Ramp length in plan
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Checks
Gradients from IStructE, Design recommendations for multi-storey and underground car parks, 3rd edition (2002), Table 4.4 and §4.3.7. Headroom of 2.10 m minimum (2.60 m for high-top vans for disabled users) applies on ramps too, measured square to the slope.
Your parking module
Module width (stall + aisle + stall)
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Accessible parking (2010 ADA Standards)
Aisle widths: IStructE (2002) Table 4.3 for 90°, 60° and 45°, and GaVO Baden-Württemberg §4 for 30°. Stall depth is measured square to the aisle (length × sin angle + width × cos angle), wall to aisle.
These are model-code and guidance values. Check against your local code: Egyptian, Saudi (SBC), UAE and other Gulf codes and your authority may set different slopes, landing sizes, stall sizes and accessible parking counts. Have the design verified by a qualified professional.
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Pick the calculator
Choose an accessible pedestrian ramp, a car park ramp or a parking layout, and work in millimetres and metres or inches and feet.
Enter the rise or the stall
Type the total rise and the slope, or the stall size, parking angle, aisle traffic and row length. Feet-inches like 2′ 6″ and slopes like 1:12 or 8.33% both work.
Read the layout and checks
You get the run length, runs, landings and slope in %, degrees and 1:n, or the module width, stalls and area per car, with a scaled drawing and pass/fail checks against the cited standard.
How to calculate ramp length and parking module width
A ramp’s horizontal length is its rise divided by the slope. Under the 2010 ADA Standards a single run may rise at most 30″ (760 mm), so longer ramps are split into runs with level landings between them.
Runs = rise ÷ 30″, rounded up
Total length = run length + (runs − 1) × 60″ landing
Worked example: a 900 mm rise at 1:12 needs 900 × 12 = 10.8 m of ramp. 900 ÷ 762 = 1.18, so 2 runs of 5.4 m with one 1.525 m landing between them: 12.3 m in total, plus the top and bottom landings.
Total length = rise ÷ s + t
Parking module = 2 × (L × sin θ + W × cos θ) + aisle
A 3.0 m rise at 15% is 3.0 ÷ 0.15 + 3.0 = 23.0 m long. A 90° module of 2.5 × 5.0 m stalls with a 6.95 m two-way aisle is 5.0 + 6.95 + 5.0 = 16.95 m wide.
Angled stall depth is measured square to the aisle from the stall’s far corner, the same way the IStructE bin widths are built up.
ADA ramp, car park ramp and parking aisle values
| Rule | Value | Source |
|---|---|---|
| Ramp running slope | 1:12 (8.33%) max | ADA 2010 §405.2 |
| Rise per ramp run | 30″ (760 mm) max | ADA 2010 §405.6 |
| Landing length | 60″ (1525 mm) min, top and bottom of each run | ADA 2010 §405.7 |
| Ramp clear width | 36″ (915 mm) min between handrails | ADA 2010 §405.5 |
| Handrails | Both sides where a run rises more than 6″ (150 mm) | ADA 2010 §405.8 |
| Straight car ramp | 1:10; 1:6 where the rise is 1.5 m or less, with transitions | IStructE 2002, Table 4.4 |
| Curved car ramp | 1:10 up to 3.0 m rise, 1:12 above, on the centre line | IStructE 2002, Table 4.4 |
| Transitions | 3.0 m min at half the slope, where steeper than 1:10 | IStructE 2002, §4.3.7 |
| Aisle, 90° | 6.95 m two-way, 6.00 m one-way | IStructE 2002, Table 4.3 |
| Aisle, 60° / 45° one-way | 4.20 m / 3.60 m | IStructE 2002, Table 4.3 |
| Aisle, 30° | 3.0 m | GaVO Baden-Württemberg §4 |
| Accessible parking | 1 per 25 up to 100 spaces, then by Table 208.2; 1 in 6 van-accessible | ADA 2010 §208.2, §208.2.4 |
Model-code and guidance values. Egyptian, Saudi (SBC), UAE and other local codes may differ, so always check the code that applies to your project.
Ramp and parking questions
Multiply the rise by the slope ratio. At the ADA maximum of 1:12, every 1″ of rise needs 12″ of ramp, so a 24″ rise needs 24 ft and a 600 mm rise needs 7.2 m. Add a 60″ (1525 mm) landing at the top and bottom, and between runs where the rise is over 30″.
1:12, which is 8.33% or about 4.76°, under 2010 ADA Standards §405.2. Cross slope may not exceed 1:48. A surface at 1:20 or flatter is not a ramp under the ADA, so it needs no ramp handrails or landings.
A single run may rise at most 30″ (760 mm), ADA §405.6. At 1:12 that is a 30 ft (9.1 m) run. Beyond that you need a level landing at least 60″ long and as wide as the ramp before the next run starts.
The IStructE car park guide recommends 1:10 (10%) for straight ramps and 1:12 for long curved ramps, and allows up to 1:6 on short ramps rising 1.5 m or less. German garage regulations cap ramps at 15%. Ramps steeper than 1:10 need 3 m transitions at half the slope at the top and bottom so cars do not ground.
A common metric stall is 2.5 × 5.0 m, and the IStructE guide uses 2.4 × 4.8 m. At 90° a two-way aisle of about 6.95 m (6.0 m one-way) gives a module of about 16.5–17 m. Angled 60° and 45° stalls use narrower one-way aisles of 4.2 m and 3.6 m, but need more floor area per car.
Under ADA Table 208.2 you need 1 accessible space for 1–25 spaces, 2 for 26–50, up to 9 for 401–500, 2% of the total for 501–1,000, and 20 plus 1 per 100 over 1,000. One in every 6 accessible spaces, or fraction of 6, must be van-accessible.
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