By Zencalcy Editorial TeamLast reviewed About us
A ladder set too steep will tip backward; set too shallow, the feet will slide out. The 4:1 rule fixes the geometry: for every four feet of height the ladder reaches, the base sits one foot out from the wall — about 75 to 76 degrees from the ground.
Safe ladder setout angle and base distance.
working height = ladder length − 3 ft base = working height ÷ 4 angle = atan(working height ÷ base)
The 4:1 rule applies to the usable ladder length: extend the top three feet above the landing for handhold, and the safe working height is the ladder length minus those three feet. On soft ground, use levelers rather than stacking boards under the feet.
| Symbol | Meaning |
|---|---|
| L | Ladder length in feet. |
| b | Base distance from the wall. |
| θ | Angle from the ground. |
Base sits 6.25 ft from the wall at about 76°, with a 25 ft safe working height once the top three feet clear the landing.
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One foot out for every four feet of working height — the 4:1 rule. A 28 foot ladder with a 25 foot working height sets its base 6.25 feet from the wall.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026