How to use the concentration unit converter
- Enter the concentration and choose its unit from the list: grams, milligrams, micrograms or nanograms per liter, percent weight per volume, ppm, ppb, or molar units.
- If you are converting to or from a molar unit, enter the molar mass of the substance in grams per mole.
- Read the summary of the value in milligrams per liter, grams per liter, percent weight per volume and moles per liter.
- The table shows the same concentration in every unit. Units that need the molar mass say so until you enter it.
Formula
everything is converted to grams per liter first
mg/L = g/L x 1,000, ug/L = g/L x 1,000,000
percent w/v = g/L / 10 (grams in 100 mL)
mol/L = g/L / molar mass
ppm = mg/L and ppb = ug/L for dilute water solutions
The ppm and ppb rows assume the solution has the density of water, about 1 kg per liter. That holds for dilute water solutions only.
Drinking water and a salt solution
10 mg/L is 0.01 g/L, 0.001 percent weight per volume, 10 ppm and 10,000 ug/L. A concentration of 5 mg/L is 0.005 g/L and 5,000 ppb. With a molar mass of 58.44 g/mol, 5 mg/L is 0.0856 mM.
A salt solution of 0.9 percent weight per volume is 9 g/L, which is 9,000 mg/L. With the molar mass of table salt, 58.44 g/mol, that is 9 / 58.44 = 0.154 mol/L, or 154.0 mM. Converting all the units back to grams per liter gives the original 9 g/L for each, which was checked for every pair of units.
Weight per volume, molarity and parts per million
Weight per volume units tell you how many grams of the substance are in a liter or 100 mL of solution. Molarity counts molecules instead of grams, so you need the molar mass to switch between them. Parts per million is a ratio, and for dilute water solutions it equals milligrams per liter, which is why labs use the two interchangeably for water.
Where to take care
For solutions that are not dilute, or liquids that are not water, ppm by weight is no longer the same as milligrams per liter, and a density correction is needed. Some fields also use ppm for volume ratios. Check what your method means by ppm before relying on the conversion. After converting, you can dilute with the Solution Dilution Calculator or find the pH of an acid with the pH and Weak Acid Calculator.
More tools for brewing and the lab bench
For related work with solutions and concentrations, try the Mash Strike Water Calculator, SRM Beer Color Calculator and Hemocytometer Cell Count Calculator.
Assumptions and limits
- Concentrations are per liter of solution.
- Parts per million and per billion mean milligrams and micrograms per liter of a dilute water solution.
- The molar mass is the mass of one mole of the substance in grams, and it is needed only for molar units.
- The conversion is exact apart from rounding to six significant digits.
- The concentration and molar masses in the form are examples to replace with your own.
Frequently asked questions
Is ppm always the same as mg/L?
Only for dilute water solutions, where a liter weighs about a kilogram. For other liquids the two differ by the density, so a correction is needed.
How do I find the molar mass?
Add up the atomic masses of all the atoms in the formula, from the periodic table. For table salt, NaCl, sodium is about 22.99 and chlorine about 35.45, giving 58.44 g/mol.
What does percent weight per volume mean?
It is the grams of substance in 100 milliliters of solution. A 0.9 percent solution has 0.9 grams in each 100 mL, or 9 grams in a liter.
Why does the page show micromoles and millimoles?
Lab solutions are often very dilute, so millimolar and micromolar units give numbers that are easy to read. They are just thousandths and millionths of a mole per liter.