We have built two free calculators for crane operators, lift planners and plant hire contractors. Both are available on our website with no login required. This guide explains what each tool does, who should use it, and walks through a worked example for each.
Two Tools. Two Different Questions.
The Pad Size Calculator answers: which pads meet the entered screening criteria? The Ground Bearing Calculator answers: what average pressure does this pad apply?
Pad Size Calculator
Use when ordering pads. Designed for hire desks, operators and transport managers who want a shortlist to check against their site and machine requirements.
Ground Bearing Calculator
Use when screening a pad for a specific lift or preparing documentation for an Appointed Person. Designed for lift planners and crane supervisors.
Pad Size Calculator — How to Use It
Step 1: Enter the maximum design outrigger reaction in tonnes. Use the value for the exact machine configuration and duty from the manufacturer, lift plan or appointed person. Gross vehicle weight divided by the number of outriggers is not a safe substitute; if the reaction is unavailable, stop and obtain it before sizing pads.
Step 2: Enter the assessed allowable bearing pressure in kN/m². Use the value for the actual support location and record its source or reference. If it is unknown, obtain a competent ground or structural assessment before choosing a pad for use. The separate ground examples are illustrative screening inputs; a surface description does not establish its capacity.
The current calculator screens at 80% utilisation of the entered bearing limit (25% more area than the raw bearing-area calculation) to its indicative bearing-area result, then shows the smallest product in each qualifying range that also meets the manufacturer-listed pad capacity. Product cards link to the relevant page. The result remains a screening recommendation, not lift approval.
Worked Example: For illustration, with a verified 18-tonne outrigger reaction and an assessed allowable bearing pressure of 300 kN/m², the strict arithmetic area is 18 × 9.81 ÷ 300 = 0.59m². Dividing by 0.8 gives a screening area of 0.74m² — 25% more than the raw calculation. An 800×800mm square pad provides 0.64m² and therefore does not meet the headroom result; a 1000×1000mm square pad provides 1.00m² and can be shown only if its manufacturer-listed pad capacity also exceeds 18 tonnes.
Free Tool
Pad Size Calculator
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Ground Bearing Calculator — How to Use It
Step 1: Select a pad from the dropdown (grouped by Essential, Square, Round, Large Format) or enter custom dimensions for any pad not in the range.
Step 2: Enter the maximum outrigger load in tonnes for the actual machine configuration and duty, from the manufacturer, lift plan or responsible competent person.
Step 3: Enter the bearing limit. Use a verified site or structural value and record its source where available. If you use an indicative preset, treat the output as screening only and use the weakest relevant condition.
Results: Pass (green) means average pressure is no more than 80% of the entered bearing limit. Marginal (amber) is above 80% but no more than 100%. Fail (red) exceeds the entered limit. A separate pad-rating message checks the entered load against the website-listed product capacity; neither result verifies the complete lift arrangement.
Worked Example: For a verified 40-tonne outrigger reaction on a 1000×1000×60mm square pad, average pressure is 40 × 9.81 ÷ 1.00 = 392.4 kN/m². Against a 150 kN/m² input this fails. A 2000×1200mm pad has 2.4m² area, so pressure would still be 163.5 kN/m² and would also fail. The screening area at 80% utilisation is 392.4 ÷ (0.8 × 150) = 3.27m². Heavy Lift and modular arrangements are not automatically approved by the calculator and require project-specific engineering review.
Free Tool
Ground Bearing Calculator
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The Formula Behind Both Tools
Ground Pressure (kN/m²) = Load (kN) ÷ Pad Area (m²)
The Pad Size Calculator works this formula in reverse and divides the raw area by 0.8, giving 25% more area. The Ground Bearing Calculator works it forward to find average pressure. Its ground-pressure screen passes at no more than 80% of the entered bearing limit, is marginal above 80% up to 100%, and fails above 100%. Pad structural capacity is reported as a separate check.
When to Use Which Tool
Use the Pad Size Calculator for an indicative bearing-area and product screen. Use the Ground Bearing Calculator to screen a specific pad against an entered bearing limit. The outputs can support site planning records, but they do not replace the lift plan, manufacturer instructions, ground assessment or approval by the responsible competent person.
Both tools are free, require no login, and work on desktop and mobile. Candidate product links are available before entering an email address. Use Request a quote with this result to carry the calculation, source reference and candidate links into the contact form, then add the quantity, delivery postcode and required date. Use Print / save PDF for your planning record. Review every input and the separate pad-rating check before relying on the record.
Try the Free Calculators
No login required. Works on desktop and mobile. Results link directly to the CPS product pages.
