Ladder Angle Calculator
Find the ladder length you need, how far the feet go from the wall and how high a ladder reaches at a safe 75° angle.
A geometry guide for setting up a leaning ladder. Always follow the ladder manufacturer’s instructions, stand it on firm, level ground and secure it against slipping.
About this tool
Enter the height you need to reach — a gutter, a roof edge or a window — or the length of your ladder, and see how far out from the wall the feet should stand, how high the ladder reaches and how long it must be. The default is the recommended angle of about 75°, close to the 4-to-1 rule, and you can add 1 m (3 ft) so the ladder sticks up above the landing when you climb onto a roof.
Frequently asked questions
About 75° to the ground. The 4-to-1 rule gives almost the same: move the feet 1 m out from the wall for every 4 m of height, which is an angle of 75.96°. For a ladder resting 4 m up the wall, the feet should be 1.07 m out at 75° and 1.00 m out with the 4-to-1 rule.
At least 1 m when you use the ladder to climb onto a roof or a landing, according to the Danish Working Environment Authority. US OSHA rules (29 CFR 1926.1053) require the side rails to extend at least 3 ft (0.9 m) above the upper landing. For a roof edge 4 m up at 75°, that means a ladder of 4.14 m + 1 m = 5.14 m.
Divide the height by sin 75° (0.966), which adds about 3.5 %: 3 m needs 3.11 m of ladder and 6 m needs 6.21 m, plus 1 m if you climb off at the top. On an extension ladder the overlap between the sections does not count, so a ladder is always shorter in use than its fully extended length.
Use the 4-to-1 rule: measure the height to where the ladder rests and place the feet a quarter of that distance from the wall — 1.25 m for 5 m. Many ladders also have an angle indicator on the side rail. Always stand the ladder on firm, level ground and secure it against slipping.
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