Convert between slope angle in degrees and percent grade.
百分比 = tan(θ)×100。
| Item | Formula / Note | Source / Standard |
|---|---|---|
| Percentage grade | Percentage grade = tan(alpha) × 100% | JTG D20-2017, Design Specification for Highway Alignment |
| Angle from percentage | alpha = arctan( percentage / 100 ) | JTG D20-2017, Design Specification for Highway Alignment |
| Per-mille grade in railways | Railway profiles commonly express gradient in per mille (‰) | TB 10098-2017, Code for Design of Railway Line |
| Small-angle approximation | For gentle grades i ≈ alpha in radians; the approximation fails for steep grades | JTG D20-2017, Design Specification for Highway Alignment |