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Calculation Machine

Ladder Angle Calculator

Safe base distance for a ladder using the 4-to-1 rule.

Reviewed by James Whitfield · How we check our maths

Your values

ⓘ Live results

Results
Base distance from wall
4 ft
Ladder length needed
16.49 ft
Climbing angle
76° (target ~75°)

Quick answer

The safe base distance is one quarter of the ladder's working height, giving a climbing angle of about 75 degrees.

The formula

base distance = working height / 4; angle = arccos(base/ladder length)

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Working height (support point)16 ft

Result

  • Base distance from wall4 ft
  • Ladder length needed16.49 ft
  • Climbing angle76° (target ~75°)

How to use the Ladder Angle Calculator

  1. 1Measure the working height where the ladder contacts the wall or roof edge.
  2. 2Apply the 4-to-1 rule: move the base out 1 foot for every 4 feet of height.
  3. 3Check the resulting angle is close to the recommended 75 degrees.

Frequently asked questions

Why 75 degrees?

It's the angle found to balance stability against tipping backward and sliding out at the base.

What if my base distance is different?

Too shallow (base too close) risks the ladder tipping backward; too wide risks the base sliding out.

About this calculator