Ladder length calculator
Estimate base offset and ladder length using four units vertically up for every one unit horizontally out.
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Check this tool fits your task
Geometry for a straight leaning ladder on level ground. This UK-style rule is an approximation, not a complete ladder-selection or safe-access assessment.
Your result
Enter your values, or try the example to see how it works.
Calculation breakdown
What to do next
Method and sources
Offset = support height ÷ 4. Length to support = √(height² + offset²). Add projection × length-to-support ÷ height for extra ladder length.
How to use this tool
- Check the scope and collect measured or verified input values.
- Enter values using the displayed units, then calculate.
- Read the result, calculation breakdown and next steps together.
Worked example
Support height 4 m and vertical projection 1 m → base offset 1 m, working length 4.12 m, total geometric length 5.15 m.
The example button fills illustrative values. Where a scope confirmation is shown, check it yourself before calculating.
Method and references
Offset = support height ÷ 4. Length to support = √(height² + offset²). Add projection × length-to-support ÷ height for extra ladder length.
Geometry for a straight leaning ladder on level ground. This UK-style rule is an approximation, not a complete ladder-selection or safe-access assessment.
Common questions
Why does the calculation show about 76° rather than exactly 75°?
Four units vertically up and one out gives arctan(4), about 75.96°. HSE describes this practical rule as about 75°.
Can I buy a ladder of exactly the calculated length?
Check usable extended length, required section overlap, labels, task and access requirements with the supplier.
Is this the US OSHA working-length rule?
No. This page explicitly uses the UK vertical-up rule. Do not mix the two reference lengths.
Public beta · Check the method and inputs with a competent reviewer before operational use.
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