**We all that how important to know the level in the tank especially when in an old installation where pressure gauge is installed below the tank to measure pressure than by a simple calculation we can know the level.**

**Nowadays pressure transmitter does everything and shows us directly level by doing some parameter adjustment but it is still important to know how exactly calculation is done.**

**Here the pressure is given by,**

** P = (S.G.) * H ----------(1)**

** Where,**

** P is pressure**

** S.G. is the specific gravity of a liquid**

** H is the height (Level) which we have to calculate**

**Let consider pressure gauge is showing us 20 psi(P).**

**Here our tank is open so two different pressure exists one is due to the liquid and other is due to the atmosphere. so,**

** P = P(liquid) + P(atm)**

** 20 = P(liquid) + 14.69595**

** P(liquid) = 5.30405 psi**

**Now let convert it into mmH2o**

**so,**

**P(liquid) = 5.30405 * 703 (1 psi = 703 mmH2o) **

**P(liquid) = 3728.74715 mmH2o**

**Now put all the value in the equation (1)**

** P = (S.G.) * H**

** 3728.75 = 1 * H**

** H = 3728.75 mmH20**