Enter the total grams of dissolved salts and the total grams of seawater into the calculator to determine the salinity.

Salinity Formula

The following formula is used to calculate a salinity in ppt. 

S = MS / MSW *1000
  • Where S is the salinity (grams of salt per 1000 grams of seawater) (ppt)
  • MS is the mass of the salts (grams)
  • MSW is the mass of the salt water (grams)

To calculate the salinity, divide the mass of salt by the mass of water, then multiply by 1000 to express as parts per thousand.

Salinity Definition

What is salinity?

Salinity is defined as the amount of salt, in mass, in a given unit of water. The water is often referred to as saltwater or seawater.

If there are 5 grams of salt in 1000 grams of seawater, the salinity in parts per 1000 would be 5ppt.

Example Problem

How to calculate salinity?

  1. First, determine the number of grams of salt in the body of water.

    This is usually done by evaporating the water and measuring the mass of salt left. For this example, the mass of the salt is 5 grams.

  2. Next, determine the mass of the seawater.

    In this case, there were 5000 grams of seawater.

  3. Finally, calculate the salinity.

    Using the formula above, the salinity is calculated to be:
    S = MS / MSW *1000
    S = 5 / 5000 *1000
    S = 1 PPT
    The salinity is 1 gram of salt per 1 thousand grams of seawater.