Ladder Safe Angle (4:1 Rule)
For every 4 ft of height, base is 1 ft from wall. Angle ≈ 75.5°.
Result
Base distance from wall
4.85 ft
Ladder reaches 19.40 ft up. Angle: 75.96°.
- Ladder length20 ft
- 4:1 rule angle75.964°
- Base from wall4.85 ft
- Height reached19.40 ft
- Top extension3 ft above landing for safety
Step-by-step
- 4:1 rule: vertical:horizontal = 4:1.
- Diagonal (ladder) = √(4² + 1²) = √17 per unit.
- For ladder L: base = L/√17 = 4.85 ft; height = 4L/√17 = 19.40 ft.
How to use this calculator
- Enter ladder length.
About this calculator
OSHA-recommended ladder placement: 4:1 ratio. For every 4 ft of vertical height, 1 ft of horizontal base distance. Equivalent angle: arctan(4) ≈ 75.96° from horizontal. Too steep: tips backward. Too shallow: slides out. Top should extend 3 ft above landing for grip. Verify ladder is on stable ground + tied off where possible. Source: OSHA 1926.1053.
Frequently asked
Standard safety guideline. Steep enough ladder doesn't slide; not so steep it tips back.
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