🧪Concentration Converter
Enter the solute's molar mass and solution density, then a concentration in any unit, to convert to the rest.
Free Concentration Converter
This concentration converter switches between the four most common ways chemists express concentration: molarity (mol/L), molality (mol/kg solvent), mass percent (%), and parts per million (ppm). Because these units measure different physical quantities, converting between them requires the solute's molar mass and — for molarity — the solution's density.
Enter your known concentration in any one unit, along with molar mass and density, and the calculator computes the equivalent value in all three other units simultaneously. All conversions route through mass percent as a common intermediate.
Useful for lab work, solution prep, and coursework switching between concentration conventions. Free, runs entirely in your browser.
About the Concentration Converter
Features
Four concentration units
Molarity, molality, mass percent, and ppm.
Convert from any unit
Enter any one value and get the other three.
Uses density and molar mass
The proper physical link between mass- and volume-based units.
Instant, private
Runs entirely in your browser. No data is sent anywhere.
Frequently Asked Questions
What's the difference between molarity and molality?
Molarity (mol/L) is moles of solute per liter of solution; molality (mol/kg) is moles of solute per kilogram of solvent only. Molality doesn't change with temperature since it's mass-based, while molarity does since volume expands with heat.
Why do I need density to convert to molarity?
Molarity is based on solution volume, but mass percent and molality are mass-based. Density is what links mass to volume, so it's required to convert between them.
What is mass percent (%w/w)?
Mass percent is the mass of solute divided by the total mass of the solution, times 100 — for example, a 10% w/w salt solution has 10 g of salt per 100 g of total solution.
What does ppm mean?
Parts per million (ppm) is mass percent multiplied by 10,000 — it's just a more convenient scale for very dilute solutions, where percent values would be tiny fractions.
Why do I need the solute's molar mass?
Molarity and molality are both defined in moles, while mass percent and ppm are mass-based. Molar mass is the conversion factor between mass and moles for a given substance.
Can I use this for gas concentrations?
No, this calculator is designed for liquid solutions using mass and volume-based units. Gas concentrations typically use mole fraction or partial pressure instead.
What if my mass percent comes out over 100%?
That signals your inputs are inconsistent — for example, a molarity too high for the given density and molar mass to be physically possible. Double-check your values.
Does temperature affect these conversions?
Density (and therefore molarity) is temperature-dependent, so results are only as accurate as the density value you enter for that specific temperature. Molality and mass percent aren't affected by temperature.
Which unit should I use for lab work?
Molarity is most common for everyday lab solution prep since it's volume-based and easy to measure with a volumetric flask. Molality is preferred when temperature will change, such as in colligative property calculations.
Is this calculator free to use?
Yes, completely free with no sign-up, and it runs entirely in your browser.