🪜 Ladder Angle Calculator
Find the safe base distance, angle, and minimum ladder length for the height you need to reach, using the standard 4-to-1 ladder safety rule.
What this calculator does
The ladder angle calculator finds the safe base distance from the wall, the resulting ladder angle, and the minimum ladder length needed to reach a given height, following the widely used 4-to-1 ladder placement rule.
The formula
The 4-to-1 rule (recommended by OSHA and ANSI for extension ladders) says the base of the ladder should sit 1 foot away from the wall for every 4 feet of height reached, which works out to a climbing angle of about 75.5 degrees — the angle generally considered safest against slipping or tipping backward. The calculator finds that base distance, uses the Pythagorean theorem to find the ladder’s diagonal length, and adds your chosen extension length (commonly 3 feet, so the ladder extends safely above a roofline or platform).
Always inspect your ladder, footing, and surroundings before climbing, and follow the ladder manufacturer’s specific safety instructions.