Crane Outrigger Pad Calculator
CalculatorsSize crane outrigger pads from the outrigger load and the ground's allowable bearing pressure.
Not sure what to check first? Hand the result to the assistant.
About this tool
An outrigger concentrates a huge share of a crane's load onto a small float, and the ground under it fails long before the crane does. This tool sizes the pad or cribbing: it divides the load on one outrigger by the ground's allowable bearing pressure to give the minimum pad area, plus the equivalent square side and round diameter.
Enter the load on the most heavily loaded outrigger - read it from the crane's load chart or outrigger reaction chart for your configuration, radius, and quadrant - then pick the ground type (or enter a known allowable pressure). Optionally enter a pad size you have on the truck to check whether it stays within the allowable pressure.
This intentionally does not guess the outrigger load from the crane's gross weight: real reactions are wildly uneven and peak when lifting over a corner, so a guess would under-size the pad. Bring the chart number. Allowable ground pressures here are typical planning values - soft, wet, filled, or disturbed ground needs a qualified geotechnical assessment.
Frequently asked questions
How do I find the load on a crane outrigger?
From the crane's load chart or the outrigger reaction chart in the operator's manual / lift-planning software, for your exact configuration, boom radius, and the quadrant you're lifting in. Load-moment systems on many cranes also display live outrigger reactions.
Why not calculate it from the crane's total weight?
Because outrigger loads are not an even split. Lifting over a corner can put a large majority of the combined crane-plus-load weight onto a single outrigger. Estimating from gross weight would under-size the pad and is unsafe, so this tool requires the chart value.
What allowable ground pressure should I use?
Use the value from a site or geotechnical assessment when you have one. The presets are typical presumptive values (soft clay ~50 kPa, compacted gravel ~200–300 kPa, rock much higher) for planning only. When in doubt, assume weaker ground and use a bigger pad.
Are square or round outrigger pads better?
Either works - the tool gives both the square side and round diameter for the same area. Steel or engineered cribbing pads spread load better than timber; make sure the pad itself is rated for the point load from the float.
Does a bigger pad always help?
Up to a point - the pad must be stiff enough to spread the load across its whole area rather than punching through in the middle. Very large timber mats can flex; that's why engineered outrigger pads specify a load rating, not just an area.