Unit Converters · Browser · Free

ppm to mg/L Conversion Calculator

This converter switches between parts per million (ppm) and milligrams per liter (mg/L) for a water solution, and can also go from molar concentration (mol/L) to mg/L and ppm. It calculates when you press Convert and shows the results in cards below the button.

About this converter

In the Conversion mode box, choose Parts per million (ppm) to mg/L, Milligrams per liter (mg/L) to ppm, or Molarity (mol/L) to mg/L and ppm. Enter the value the mode asks for — Parts per million, Milligrams per liter, or Molar concentration together with Solute molar mass — set Water temperature, and press Convert.

Results appear in cards below the button. The Copy button writes a result and its unit to the clipboard, and Clear resets the form. Everything runs in the browser and nothing is uploaded.

Why water temperature matters

ppm is a mass-based measure (mg/kg), while mg/L is milligrams per liter of water, so moving between the two depends on the density of the water at your temperature. In this tool, 1000 ppm converts to about 998.2071 mg/L at 20 °C but about 999.972 mg/L at 4 °C, and 1000 mg/L at 20 °C converts back to about 1001.79612026402 ppm.

Conversion formula

Parts per million (ppm) to mg/L: multiply the ppm value by the density of water in g/L at your temperature and divide by 1000. For example, C(mg/L) = 1000 ppm × (998.2071 g/L) / 1000 ≈ 998.2071 mg/L at 20 °C.

Milligrams per liter (mg/L) to ppm: multiply the mg/L value by 1000 and divide by the density of water in g/L. For example, C(ppm) = 1000 × 1000 mg/L / (998.2071 g/L) ≈ 1001.79612026402 ppm at 20 °C.

Molarity (mol/L) to mg/L and ppm: multiply the molar concentration (mol/L) by the solute molar mass (g/mol) and by 1000 to get mg/L, then convert to ppm at the entered temperature. For example, c = 0.01 mol/L × 58.44 g/mol × 1000 = 584.4 mg/L ≈ 585.449652682294 ppm.