Pressure is a physical quantity that expresses the force acting uniformly on a unit area perpendicular to the surface. When force acts uniformly on a flat surface, pressure is equal to the force divided by the area:
$$p=\frac{F}{S}$$
where,
F— force acting perpendicular to the surface;
S— area over which the force is applied.
The unit of pressure in the SI system is the pascal (Pa), named after Blaise Pascal. 1 Pa is the pressure or mechanical stress generated by a force of 1 N uniformly distributed over an area of 1 m2:
$$1\mathrm{Pa}=\frac{\mathrm{N}}{\mathrm{m}^{2}}=\frac{\mathrm{kg}}{\mathrm{m}\cdot \mathrm{s}^{2}}$$