In concentrations of solutions, measurements of the components are often given in parts per million (ppm). Parts in the solution could be sediments, gases, metals or contaminates in the total mixture. The solution is most often a mixture of liquids or gases. One instance this could be used is if you have to find the parts per thousand (ppt) when given parts per million (ppm) of carbon dioxide in the atmosphere.

Use the equation to convert between ppm and ppt: 1 ppm = 0.001 ppt; therefore ppt = ppm / 1,000.

Take the measurement in parts per million (ppm) and divide it by 1,000. For instance, if you have a reading of 340,000 ppm of carbon dioxide in a gas, divide it by 1,000: 340,000 ppm / 1,000

Solve the equation. In the above example: 340,000 ppm / 1,000 = 340 ppt carbon dioxide in the gas mixture

Convert ppt to ppm by multiplying ppt by 1,000. For instance, if you have 4,000 ppt sediment in water and you need ppm: 4,000 ppt x 1,000 = 4,000,000 ppm of sediment in the water