Kilopascal
Also called kPa, Kilonewtons per square metre, kN/m², Tonnes per square metre, t/m²
The unit UK ground bearing figures are written in: one kilopascal (kPa) is one kilonewton per square metre, so kPa and kN/m² are the same unit under two names. One tonne per square metre is 9.81 kPa, and one kilopascal is about 20.9 pounds per square foot — the conversion needed to read ground pressure figures published for the American market.
From our specifications
Worked on our own configurations: a 30 t outrigger reaction is 294 kN, which reaches the ground at 117 kPa under the 2.523 m² ALIMATS® configuration and at 36 kPa under the 8.074 m² one. Nothing about the crane changed between those two figures. Megapascals appear on the same datasheets and describe something else entirely — 1 MPa is 1,000 kPa, equivalently 1 N/mm², and it is a material strength rather than a pressure on the ground, so the two are three orders of magnitude apart and are not comparable numbers.
Source: alimat_configurations plan areas, worked at the 9.81 kN per tonne our crane mat calculator uses
Where it matters on site
Converting an allowable pressure into an area is the step most often skipped between a ground investigation and a mat order. Our crane mat calculator asks for the outrigger load in tonnes and the bearing area required in square metres, and that area is the load multiplied by 9.81 and divided by the allowable pressure in kPa: a 30 t reaction on ground assessed at 150 kPa needs 1.96 m², so the 2.018 m² configuration covers it and the 1.346 m² does not. Treat figures lifted from American literature with care — a number in psf is roughly twenty-one times the same pressure in kPa, and looks reassuringly large.