Wheelchair Ramp Slope Calculator

Use this wheelchair ramp slope calculator to measure the appropriate length and angle of a ramp for safe and comfortable handicap ramp access.

A building entrance with a 30-inch height difference from ground level. A handicap ramp slope / length calculator might suggest a ramp length of 30 feet to achieve a 1:12 slope ratio, which is generally considered the gold standard for wheelchair accessibility.

Wheelchair Ramp Slope Calculator

Rise (inches)	Slope Ratio	Ramp Length (inches)	Ramp Length (feet)
12	1:12	12	1
12	1:10	10	0.83
12	1:8	9	0.75
24	1:12	24	2
24	1:10	20	1.67
24	1:8	18	1.5
36	1:12	36	3
36	1:10	30	2.5
36	1:8	27	2.25
48	1:12	48	4
48	1:10	40	3.33
48	1:8	36	3
60	1:12	60	5
60	1:10	50	4.17
60	1:8	45	3.75
72	1:12	72	6
72	1:10	60	5
72	1:8	54	4.5
84	1:12	84	7
84	1:10	70	5.83
84	1:8	63	5.25
96	1:12	96	8
96	1:10	80	6.67
96	1:8	72	6

Wheelchair Ramp Slope Formula

The formula for calculating wheelchair ramp slope is:

Slope Ratio = Rise : Run

Where:

• Rise is the vertical height difference
• Run is the horizontal length of the ramp

This ratio is typically expressed as 1:X, where X represents the horizontal distance required for every 1 unit of vertical rise. For instance, a slope of 1:12 means that for every 1 inch of rise, the ramp extends 12 inches horizontally.

To calculate the required ramp length, use this formula:

Ramp Length = Rise × Slope Ratio

For example, if you have a 24-inch rise and want a 1:12 slope: Ramp Length = 24 inches × 12 = 288 inches (24 feet)

How Long Should a Ramp Be for 24 Inches?

Using the ADA-recommended 1:12 slope:

• 1:10 slope: 24 inches × 10 = 240 inches (20 feet)
• 1:8 slope: 24 inches × 8 = 192 inches (16 feet)

For a 24-inch rise, the ideal ramp length depends on the desired slope ratio.

Ramp Length = 24 inches × 12 = 288 inches (24 feet)

How Long Should a Ramp Be for a 3-Foot Rise?

Using the preferred 1:12 slope:

• 1:10 slope: 36 inches × 10 = 360 inches (30 feet)
• 1:8 slope: 36 inches × 8 = 288 inches (24 feet)

A 3-foot (36-inch) rise requires careful consideration to ensure accessibility.

Ramp Length = 36 inches × 12 = 432 inches (36 feet)

What is the Proper Slope for a Wheelchair Ramp?

The widely accepted standard is a 1:12 slope ratio.

This 1:12 ratio strikes a balance between accessibility and practicality:

• It’s gentle enough for most wheelchair users to navigate independently
• It minimizes the risk of tipping or losing control
• It complies with ADA (Americans with Disabilities Act) guidelines for public buildings

In some cases, slightly steeper slopes may be permissible:

• 1:10 for short ramps (up to 6 inches of rise)
• 1:8 for very short ramps (up to 3 inches of rise) in residential settings

How Long Should a Ramp Be for 4 Steps?

Assuming standard step heights of 7 inches:

• 1:10 slope: 28 inches × 10 = 280 inches (23.33 feet)
• 1:8 slope: 28 inches × 8 = 224 inches (18.67 feet)

To determine the appropriate ramp length for 4 steps, we first need to calculate the total rise.

Total Rise = 4 steps × 7 inches = 28 inches

Now, applying the recommended 1:12 slope ratio:

Ramp Length = 28 inches × 12 = 336 inches (28 feet)

References

• ADA.gov – 2010 ADA Standards for Accessible Design: https://www.ada.gov/2010ADAstandards_index.htm
• U.S. Access Board – Ramps and Curb Ramps: https://www.access-board.gov/ada/guides/chapter-4-ramps-and-curb-ramps/
• National Council on Independent Living – Ramp Projects: https://ncil.org/ramp-projects/

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