Outrigger ground pressure calculator
This page reports what the official source says. It is not legal advice: ask the office named here. Type the load on one pad and the area of the pad to see the pressure on the ground under it, in pounds-force per square inch, pounds-force per square foot and kilopascals. OSHA, whose crane rule on ground conditions is cited here, is the office named here.
Checked against the sources at the bottom of this page on October 8, 2026. Published tables are revised: the source has the last word.
Work it out
How the answer is worked out
Pressure = the load divided by the area. The load is changed to newtons and the area to square metres, which gives pascals, and the pascals are then shown in the three units.
1 pound-force per square inch is 6.894757 kilopascals, and 1 pound-force per square foot is 47.88026 pascals, as NIST prints them. 1 kilogram-force is 9.80665 newtons.
What the sources say
OSHA's crane rule on ground conditions, 29 CFR 1926.1402, defines ground conditions as the ability of the ground to support the equipment, including slope, compaction and firmness. It defines supporting materials as blocking, mats, cribbing, marsh buggies or similar materials or devices. It says the equipment must not be assembled or used unless the ground is "firm, drained, and graded" enough that, with supporting materials where needed, the manufacturer's specifications for adequate support and level are met.
The same rule says that when the assembly and disassembly director or the operator finds the ground does not meet that requirement, that person's employer must discuss with the controlling entity the ground preparations needed, with suitable supporting materials if necessary.
NIST lists pressure as force divided by area in its Appendix B.9 factors by kind of quantity, with the pound-force per square inch, the pound-force per square foot and the kilogram-force per square centimetre among its entries.
The page does not say what pressure any ground can carry, how a mat spreads a load or what a load chart allows. The load box takes a force, and a load typed in kilograms-force is changed at NIST's 9.80665 newtons to the kilogram-force.
Arithmetic only. The answer is only as good as the numbers entered. It is not a plan or a safe working load for any job.
Sources
- OSHA, 29 CFR 1926.1402 Ground conditions (cranes and derricks in construction), read October 8, 2026
- NIST, Guide for the Use of the International System of Units (SP 811), Appendix B.8 factors for units listed alphabetically, read October 8, 2026
- NIST, Guide for the Use of the International System of Units (SP 811), Appendix B.9 factors for units listed by kind of quantity, read October 8, 2026
- NIST, Guide for the Use of the International System of Units (SP 811), footnotes to Appendix B, read October 8, 2026