How do I calculate the hydrostatic pressure?

Hydrostatic pressure originates from the weight of the liquid. At a certain point in the liquid, the hydrostatic pressure is going to be equal to the weight of the liquid above the examined point.  So in order to calculate it first, we need to calculate the weight of the liquid which creates the pressure. To calculate the weight we need to know the mass of the liquid. This can be found by the following formula:

m= ρ * h

where ρ is the density of the fluid and h is the height of the fluid above the examined point. 

If we multiply this by g we find the weight of the fluid which equals the hydrostatic pressure:

P= ρ hg

To find the absolute pressure at the point we have to add up the atmospheric pressure (pressure above the fluid) and the hydrostatic pressure.

Pabs=P+Patm.