Explore extension-ladder planning geometry from support height and an entered extension, including calculated rail length and a 4:1 height-to-setback scenario.
Inputs and method
Enter support height and the desired extension above it. The planning worksheet uses a 4:1 height-to-setback geometry and adds the entered extension to the sloped rail length. The extension input is always in feet, including when support height is entered in meters. In feet mode, the planning length is rounded upward to one decimal place; meter mode converts that feet-based planning value and displays it to one decimal place.
Calculations retain full floating-point precision until the labeled display step. Counts and packages use an explicit upward ceiling only where a whole purchase unit is required.
Interpreting the estimate
Use the result as a planning value and keep input precision consistent with the measurements or source data you have. Small displayed differences can come from final-place rounding; intermediate values are not rounded.
Assumptions and limits
Geometry alone cannot determine a safe ladder, duty rating, setup, access method, or regulatory compliance. Site conditions and applicable requirements need qualified evaluation. Ladder access is commonly part of roof work, so pair the setup with the roofing calculator and roof pitch calculator; for elevated exterior painting, see the paint calculator.
Rejecting empty, invalid numeric, prohibited negative, zero-denominator, impossible, or unsupported inputs prevents the page from presenting a misleading numeric result.
Keep a geometry estimate separate from setup requirements
Save the measured geometry and any entered assumptions alongside the result. Compare a second setup only with its changed dimensions explicitly recorded. Before using a ladder, consult its instructions and applicable requirements; a calculation from entered measurements cannot verify the actual equipment, support, or worksite conditions.
Sources
- Ladders in construction, 29 CFR 1926.1053 — ladder safety requirements and guidance.
- Walking-working surfaces ladders, 29 CFR 1910.23 — ladder safety requirements and guidance.
- Ladder Safety app and fall prevention resources — ladder safety requirements and guidance.