The pressure in a fluid is defined as "the normal force per unit area exerted on a imaginary or real plane surface in a fluid or a gas"
The equation for pressure can expressed as:
p = F / A
where
p = pressure (lb/in2 (psi) or lb/ft2 (psf), N/m2 or kg/ms2 (Pa))
F = force ( N)
A = area (in2 or ft2, m2)