Ladder Height Calculator
Find the safe ladder length for any working height.
Calculates required ladder size and proper 75-degree setup angle using the 4-to-1 safety rule.
Ladder safety depends on both height selection and proper angle. Using the wrong ladder height — or leaning it at the wrong angle — is one of the most common causes of falls at home and on job sites.
Safe working angle (4:1 Rule):
Base Distance = Working Height / 4
The base of the ladder should be 1 foot away from the wall for every 4 feet of height — giving an angle of approximately 75 degrees, the OSHA-recommended working angle.
Ladder height to reach calculation:
Required Ladder Height = Reach Height − 4 ft
(Your standing reach from the top of a ladder is roughly 4 feet above the ladder’s top rung.)
Worked example: You need to clean gutters 16 feet above the ground:
- Required ladder: 16 − 4 = 12-foot ladder
- Safe base distance: 16 / 4 = 4 feet from wall
Ladder type selection guide:
| Task | Recommended Type |
|---|---|
| Indoor painting (ceiling) | 4–6 ft stepladder |
| Changing high light fixtures | 6–8 ft stepladder |
| Single-story gutter cleaning | 16–20 ft extension |
| Two-story exterior work | 24–28 ft extension |
| Multi-story / professional | 32–40 ft extension |
Weight rating classes:
- Type III (Light Duty): 200 lbs, household use only
- Type II (Medium Duty): 225 lbs, light trade use
- Type I (Heavy Duty): 250 lbs, industrial use
- Type IA (Extra Heavy): 300 lbs
- Type IAA (Special): 375 lbs
Always include your body weight plus the weight of tools and materials.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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