Comprehensive Calculator Guide
This calculator works out the slope of a ramp, road or surface from its rise and horizontal run, in three forms: a percentage, an angle in degrees and a 1:x ratio. A ramp rising 0.5 m over 6 m is 8.33%, 4.76° or 1:12 — the usual limit for wheelchair ramps. It also gives the length along the slope for tiles or concrete.
Three ways to write a slope
Percentage = rise ÷ run × 100; angle = arctan(rise ÷ run); 1:x means x units across for each unit up. A 100% slope is 45°, not vertical.
Rough guides: 1–2% to drain flat roofs and yards, up to 1:12 (8.33%) for wheelchair ramps, about 15% for car-park ramps. Follow the building code and an engineer for real designs.
How to Use
- Enter the rise — the height difference from bottom to top.
- Enter the horizontal run in the same unit, not the sloped length.
- Press “Calculate slope” to see the percentage, angle, 1:x and the sloped length.
Formula Used
Slope % = rise ÷ run × 100 | Angle = arctan(rise ÷ run)
Practical Examples
- Example 1
- 0.5 m over 6 m: 8.33%, 4.76°, 1:12; sloped length 6.02 m.
- Example 2
- 8 m over 100 m: 8%, 4.57°, 1:12.5.
Important Tips
- To design for a set slope: run = rise ÷ (percentage ÷ 100).
Common Mistakes to Avoid
- Dividing by the sloped length instead of the horizontal run.
Frequently Asked Questions
- How do I calculate slope percentage?
- Rise ÷ run × 100.
- What slope is allowed for a wheelchair ramp?
- Usually no more than 1:12, or 8.33%.
- How do I convert a slope percentage to degrees?
- Angle = arctan(percentage ÷ 100); 100% is 45°.