Ladder Angle Calculator
Set an extension ladder at the safe 4-to-1 angle: how far the feet go from the wall, and how long a ladder you need for the height.
Your results
Worked example
Reaching eaves that are 4.8 m up (a typical two-storey wall):
- Base distance: 4.8 ÷ 4 = 1.20 m from the wall
- Angle: arctan(4) = 75.96°, about 76 degrees
- Minimum ladder length: 4.8 × 1.0308 = 4.95 m to just reach the rest point
- Recommended: add 0.9 m of rail above the edge to hold onto while stepping off: 4.95 + 0.9 = 5.85 m, so a 6 m (20 ft class) extension ladder is the practical buy, remembering that extension ladders lose length to the overlap between sections
How this calculator works
The 4-to-1 rule is the standard setup taught in ladder safety training: for every 4 units of height to the rest point, the feet sit 1 unit out from the wall. Steeper than that and the ladder can tip backward; shallower and the feet can slide out or the rails can flex and slip. The recommended length adds 0.9 m (about 3 ft) of rail extending above the landing edge, the standard guidance for roof access, so you can hold the rails while stepping on and off.
Common questions
How do I check the angle without a calculator?
Stand with your toes at the ladder's feet and hold your arms straight out in front of you at shoulder height. Your palms should rest flat on a rung. If you have to reach up or down, the angle is off. Adjust the feet until the test passes, then re-check the base distance against the 4-to-1 rule.
Why is the ladder I need longer than the number shown?
Two reasons. First, an extension ladder's two sections overlap, so a ladder sold as 6 m extends to noticeably less than 6 m of working length; check the label for its maximum extended length. Second, for roof access the rails should project about 0.9 m above the edge, which the recommended figure here already includes.
Estimates only, based on the 4-to-1 rule. Ladder safety also depends on the ground surface, the ladder's condition and duty rating, tying off or footing the ladder, weather, and keeping three points of contact. Follow the ladder manufacturer's instructions and applicable safety regulations, which govern over any general guidance here. Mississippi Maple accepts no liability for falls, injuries, or decisions made using this calculator.