Compute longitudinal grade as height difference divided by horizontal distance.
坡度% = (h / d) × 100。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Grade definition | Grade i = rise ÷ run × 100% = tanα × 100% | Standard grade definition |
| Angle conversion | 1% ≈ 0.573°; 100% = 45°; grade is linear in tanα, not in the angle | Trigonometric conversion |
| Roadway limits | Expressway/class-1 max grade 3%–4% (mountainous up to 6%–8% by class) | JTG D20-2017 Table 8.2.2 |
| Accessible ramps | Wheelchair ramps ≤1:12 (8.33%); ≤1:20 preferred outdoors | GB 50763-2012 Accessibility Design Code |