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.