Free · Mixtures and solutions calculators ⚗️

Mass Percent & Density to Molar Concentration

Convert mass percentage to molarity or solve a related quantity using solution density and a preset or custom solute molar mass.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A 10% by-mass solution with density 1 g/cm³ and solute molar mass 50 g/mol contains 2 mol/L.

Molarity (mol/L) = mass percent × density (g/L) / (100 × molar mass (g/mol))

Worked example

Enter these known values and leave the other values blank.

Mass percentage (w/w)
10 %
Solution density
1 g/cm³
Custom solute molar mass
50 g/mol
Molarity
2 mol / dm³

Assumptions and limitations

  • Percentage is grams of solute per 100 grams of solution. Volume percentage and mass-per-volume percentages use different relationships.
  • Use the density of the solution at the temperature of interest, not the pure solute or solvent density. Preset molar masses are rounded reference values.
  • Mass percent ranges from 0% to 100%; density and molar mass must be positive. The zero-percent case gives zero molarity and does not uniquely determine density or molar mass.

Common questions

What assumptions matter for this calculation?

Percentage is grams of solute per 100 grams of solution. Volume percentage and mass-per-volume percentages use different relationships.

References

Bookify accepts zero mass percentage and zero molarity while preserving positive density and molar mass. The custom-mass visibility condition uses the identical numeric dataset choice. The US fluid ounce uses one 128th of the exact US liquid gallon, replacing the rounded captured reciprocal factor. Bookify replaces the captured rounded US gallon with the exact 3.785411784-liter definition. Bookify uses exact customary mass and volume definitions for density units, replacing rounded factors in the reference.

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