Pressure is defined as a force exerted on a surface, so its calculation is done by dividing the force by the surface: P = N/S.
The pascal (Pa symbol) is the standard unit defined in the International System. A pressure of 1 pascal corresponds to a force of 1 newton exerted on a surface of 1 m2:
1 Pa = 1 N m-2.
P = 124,500 N / 1.5 m2 = 83,000 N/m2 = 83,000 Pa.