Slope8.3%Ratio 1 : 12
Accessibility reference: check local accessibility standards before building or buying a ramp.
Ramp planning
01 Ramp Slope Calculator
Is this slope a sensible starting point?
A quick browser-only calculator that turns ramp length and rise into a slope percentage and ratio. Use it as a first check before consulting local accessibility standards and a qualified professional.
Tool introduction
What this tool does
The Ramp Slope Calculator takes two simple measurements — the horizontal length of a ramp and the vertical rise it needs to overcome — and instantly shows the slope as a percentage and a 1:n ratio. These two numbers are the starting vocabulary of ramp planning. A slope that looks gentle to the eye can be surprisingly steep for a wheelchair user, and a ratio that meets one standard may not meet another. The calculator gives you an objective first read so that conversations with contractors, suppliers, or building officials begin with shared numbers rather than guesses.
Why slope matters
Slope determines effort, safety, and usability. A steeper slope demands more upper-body strength to ascend and more braking control to descend. It affects wheelchair batteries, caregiver strain, and the risk of slipping on wet or icy surfaces. Most accessibility standards set a maximum running slope (often around 8.3% or 1:12) for occupied wheelchair use, but the exact figure depends on local codes, the ramp length, whether landings are present, and the type of mobility device. Knowing your slope before you build or buy lets you compare options against the rules that actually apply to your situation.
A starting point, not an approval
The calculator produces a number, not a certification. A slope within a common range does not automatically mean a ramp is safe or compliant, because the full route — landings, top and bottom clearance, handrails, surface texture, edge protection, and transition lips — must also be correct. Treat the result as a reason to ask better questions and to verify with the professional responsible for your site.
How to use
- 01
Measure the ramp length
Measure the horizontal distance from the base of the ramp to the point directly below the top edge. Enter this value in centimetres in the "Ramp length" field. If the ramp has multiple sections, measure each run separately and calculate each one.
- 02
Measure the rise
Measure the vertical height from the ground to the top of the ramp surface. Enter this in centimetres in the "Rise / height" field. For a threshold ramp, this may be only a few centimetres; for a porch, it may be much more.
- 03
Read the slope and ratio
The calculator displays the slope as a percentage (rise ÷ length × 100) and the ratio (1 : length ÷ rise). A common accessibility reference is 1:12 (≈8.3%), but always check your local standards for the exact requirement that applies to your building type and ramp length.
- 04
Compare with standards
Write down the result and compare it with local building codes, the ramp manufacturer guidance, and any relevant accessibility standard. If the slope is steeper than allowed, you may need a longer ramp, a switchback design, or a different approach entirely.
- 05
Plan landings and edge protection
If the ramp is long, plan level landings at intervals specified by your local code. Check that there is a level space at the top and bottom, and consider handrails and edge protection regardless of slope.
- 06
Verify with a professional
Before installing or using a ramp for daily occupied access, have a qualified contractor, accessibility consultant, or building official verify the design. The calculator is a conversation tool, not a substitute for professional review.
Frequently asked questions
What slope is considered accessible?
A common reference is 1:12 (about 8.3%), meaning for every 1 cm of rise you need at least 12 cm of ramp length. However, the exact requirement depends on your local building code, the ramp length, the building type, and the device being used. Shorter threshold ramps may permit steeper slopes in some jurisdictions. Always check the standard that applies to your specific situation.
Can I use this for a vehicle ramp?
Vehicle ramps and occupied-wheelchair ramps have different requirements. A vehicle ramp may be acceptable at a steeper grade for a powered chair with assistance, but you should follow the vehicle manufacturer guidance and local regulations for occupied transport. The calculator provides the mathematical slope; it does not determine whether that slope is safe for your intended use.
Does the calculator save my data?
No. The calculator runs entirely in your browser. Nothing is uploaded, stored, or sent to any server. If you close or refresh the page, the values are lost. If you need a record, write down or screenshot the results.
What if my ramp has a switchback or multiple sections?
Calculate each section separately. Measure the length and rise of each individual run, and check the slope of each one against your standard. Also ensure that the turning platform or landing between sections meets the size and slope requirements of your local code.
Why does the ratio show "1 : 12" when my slope is 8.3%?
The ratio (1:n) and the percentage are two ways of expressing the same relationship. A 1:12 ratio means 1 unit of rise for every 12 units of run, which equals 8.33%. They are mathematically equivalent. Standards may reference either format.
Do I still need handrails if the slope is gentle?
Handrail requirements depend on local code, ramp length, rise, and whether the ramp is used by people with different mobility needs. Even where not strictly required, handrails and edge protection are good practice for safety, especially on longer ramps or in wet climates. Consult a local professional for your specific situation.