Question 1

Are percent, degrees and a 1:n ratio the same number?

Accepted Answer

No. Percent = (rise ÷ run) × 100, degrees is a trigonometric angle (arctan of rise÷run), and a 1:n ratio means one unit of rise for every n units of run. For example a 10% slope ≈ 5.71° ≈ 1:10 ≈ 100‰ — different numbers for the same grade, so never mix them in a calculation.

Question 2

When should I use per-mille (‰)?

Accepted Answer

Per-mille is common for pipe drainage and railway gradients, where slopes are very small; instead of writing 0.5% you write 5‰ for readability. The tool shows the per-mille value alongside every other form.

Question 3

How do I measure rise and run?

Accepted Answer

The run is the horizontal distance between two points, and the rise is the vertical difference in elevation between them. Enter both in the same unit (metres, say) and the tool derives the slope automatically; the rise-to-run ratio is the basis of every other representation.

Question 4

Does the tool set the maximum allowed slope for ramps or roads?

Accepted Answer

No. Maximum slopes for ramps, access routes and roads vary by local building code and by country and use-case. This tool only converts values and is not legal or engineering advice — check the regulations and adopted code in your area before you build.

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Slope & grade calculator