Convert mg/L to parts per thousand by mass (ppt, g/kg) using solution density. The default 1 kg/L is a water approximation.

ppt means parts per thousand by mass (g/kg). Density defaults to 1 kg/L; use measured density for your solution.

mg/L to ppt Formula

The following formula is used to calculate the approximate value in parts per thousand from a concentration in milligrams per liter using solution density; at 1 kg/L this reduces to the water approximation.

ppt = (mg / L) / (1000 × density in kg / L)

Variables:

  • ppt here is parts per thousand by mass, or grams of solute per kilogram of solution
  • mg/L is the concentration in milligrams per liter
  • Density is the total solution mass in kg/L; 1000 converts milligrams to grams

Divide mg/L by 1000 times the solution density in kg/L. At the default density of 1 kg/L, divide by 1000. Use measured density for seawater, wastewater or other samples when accuracy matters.

What is mg/L to ppt Conversion?

Milligrams per liter (mg/L) measures the mass of solute in each liter of solution, while parts per thousand (ppt) expresses concentration as a fraction of one thousand parts. For dilute aqueous systems, 1 liter of water has a mass of about 1 kilogram, so 1,000 mg/L is approximately equal to 1 ppt. At density 1 kg/L, divide mg/L by 1000; otherwise divide by 1000 times density in kg/L.

mg/L to ppt Conversion Table

The table below assumes density 1 kg/L and uses ppt = mg/L ÷ 1000.

Concentration (mg/L) Approximate fraction Value in ppt
50 mg/L 0.00005 0.05 ppt
100 mg/L 0.00010 0.10 ppt
500 mg/L 0.00050 0.50 ppt
1,000 mg/L 0.00100 1.00 ppt
2,000 mg/L 0.00200 2.00 ppt
10,000 mg/L 0.01000 10.00 ppt

How to Convert mg/L to ppt?

The following steps outline how to convert mg/L to ppt.

  1. First, determine the concentration in mg/L.
  2. Next, enter solution density in kg/L, or retain the disclosed 1 kg/L water approximation.
  3. Then divide mg/L by 1000 times solution density in kg/L.
  4. After calculating the result, check your answer with the converter above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Concentration (mg/L) = 2,000

Solution density = 1 kg/L (water approximation)

Result (ppt) = 2.0

For another example, 50 mg/L corresponds to 0.05 ppt, while 10,000 mg/L corresponds to 10 ppt.