Ground pressure is the pressure exerted on the ground by the tires or tracks of a motorized vehicle, and is one measure of its potential mobility, especially over soft ground. Ground pressure is measured in pascals (Pa) which corresponds to the EES unit of pounds per square inch (psi). Average ground pressure can be calculated using the standard formula for average pressure: P = F/A. In an idealized case, i.e. a static, uniform net force normal to level ground at Earth sea level, this is simply the object's weight divided by contact area. The ground pressure of motorized vehicles is often compared to the ground pressure of a human foot, which can be 60 - 80 kPa while walking or as much as 13 MPa for a person in spike heels.