Construction geometry

Ramp Slope and Length Calculator

Calculate the geometric relationship between ramp rise, horizontal run, sloping length, slope percentage and angle. The ramp tool accepts two geometric dimensions or rise with a slope specification.

Open Ramp Calculator

What you can do

  • Calculate sloping length from rise and horizontal run.
  • Convert a rise-to-run ratio into percent grade and slope angle.
  • Calculate the missing rise or run when sufficient input is provided.
  • Check whether three entered geometric values are mutually consistent.

Formula and interpretation

Ramp grade is 100 × rise ÷ horizontal run, while the angle is arctan(rise ÷ run). The sloped length is √(rise² + run²) for a straight ramp. A slope written 1:12 means 1 unit of rise for every 12 units of horizontal run; do not confuse horizontal run with the sloped length.

Worked 1:12 ramp example

For rise = 0.60 m and horizontal run = 7.20 m, rise/run = 1/12. The grade is 100×0.60/7.20≈8.33%; angle≈4.76°; sloping length=√(0.60²+7.20²)≈7.225 m. These values describe geometry only—not a code-compliant accessibility design.

How to use the workspace

  1. Open Ramp Calculator and choose a pair of known dimensions.
  2. Enter rise 0.60 m and horizontal run 7.20 m.
  3. Compare the displayed grade, ratio, angle and sloping length.
  4. Use the governing local accessibility/building code to check maximum slope, landings, clear widths, handrails and context.

Assumptions and common errors

  • Code compliance: a 1:12 slope is an example, not a universal legal design allowance.
  • Landing requirements: geometry alone does not determine permissible total rise or landing spacing.
  • Units: use one consistent length unit for rise and run.

Frequently asked questions

How do I calculate slope percentage?
Divide vertical rise by horizontal run and multiply by 100.
Are a 1:12 ramp and 12% grade the same?
No. A 1:12 ratio is approximately 8.33% grade, whereas 12% grade is a ratio of about 1:8.33.
Does the tool certify accessibility?
No. It calculates geometry; code and site requirements must be checked separately.

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