はしご安全設置＆角度計算機
Calculate compliant OSHA 4:1 ladder standoff, safe ~75.96° inclination angle, and minimum working reach before climbing. Studying general right-triangle math or missing side problems? Return to our Pythagoras equation solver.
はしご安全設置＆角度計算機
OSHA 4:1 Rule: base = h / 4 · L = √(h² + base²) · θ ≈ 75.5°–76°
安全にはしごを掛けるチェックリスト
- Set ladder base 4 ft away from wall (OSHA 4:1 rule for 16 ft height).
- Verify ladder working reach L = √(16² + 4²) ≈ 16.49 ft.
- Add 3 ft roof landing extension → select ladder ≥ 19.49 ft.
- Safe OSHA Pitch (75.96°): Balanced against backward tip and base slip.
安全にはしごを掛けるチェックリスト
Measure Eave or Support Height (h)
Determine the vertical contact height. Never guess ladder reach by height alone because angling the base consumes vertical length.
Set 4:1 Base Standoff (b = h ÷ 4)
Position feet out 1 ft per 4 ft of wall height (0.25 m per 1 m). This hits ~75.96°, squarely inside the OSHA 72°–78° safe pitch band.
Include +3 ft (+0.91 m) Roof Extension
When transitioning onto a roof deck, add 3 feet past the gutter/eave line so your hands maintain three-point grip while stepping off.
Perform Elbow & Foot Check
Stand upright with toes touching the ladder rails and extend arms straight ahead—your palms should comfortably touch the rung at shoulder height (~75.5°).