Calculate molarity from solution density, weight percent, and molar mass, or reverse-solve density or composition with full unit conversion.

Density alone does not determine a soluteโ€™s molarity. Use the solution density and solute mass percent at the same conditions.

Solute mass divided by total solution mass, multiplied by 100.

Related Calculators

Density to Molarity Formula

Solution density, solute mass percent and molar mass together determine molarity. Density alone is insufficient.

M = (D ร— 1000 ร— (P / 100)) / MM

Variables:

  • M is the molarity of the solution (mol/L)
  • D is the density of the solution (g/mL)
  • MM is the molar mass of the solute (g/mol); P is solute mass percent (% w/w)

Multiply solution density in g/mL by 1000 and by the solute mass fraction (P/100), then divide by molar mass in g/mol. The simplified density-only expression applies only at 100% solute mass fraction.

Hypothetical arithmetic at 100% solute mass fraction (molar mass 58.44 g/mol); not an aqueous NaCl property table
Density (g/mL) Molarity (mol/L)
0.508.556
0.6010.267
0.7011.978
0.7512.834
0.8013.689
0.8514.545
0.9015.400
0.9516.256
1.0017.112
1.0517.967
1.1018.823
1.1519.678
1.2020.534
1.2521.389
1.3022.245
1.4023.956
1.5025.667
1.6027.379
1.8030.801
2.0034.223
* Rounded to 3 decimals. Uses M = (ฯ ร— 1000) / M_m. Assumes 100% solute mass fraction and molar mass 58.44 g/mol. These are hypothetical arithmetic examples, not realizable aqueous NaCl density/concentration pairs.

What is Molarity?

Molarity is a measure of the concentration of a solute in a solution, or the number of moles of solute per liter of solution. It is one of the most common units used to express the concentration of a solution in chemistry. Molarity is important for calculating dilutions and for performing stoichiometric calculations in chemical reactions.

How to Calculate Molarity from Density?

The following steps outline how to calculate the molarity from density.

  1. First, determine the density of the solution (D) in grams per milliliter (g/mL).
  2. Next, determine the molar mass of the solute (MM) in grams per mole (g/mol).
  3. Next, determine the solute mass percent P (% w/w), then use M = D ร— 1000 ร— (P/100) / MM.
  4. Finally, calculate the molarity (M) in moles per liter (M).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

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

Density of the solution (D) = 1.05 g/mL

Molar mass of the solute (MM) = 58.44 g/mol

For an illustrative 10% w/w composition: M = 1.05 ร— 1000 ร— 0.10 รท 58.44 โ‰ˆ 1.796715 mol/L. Density and composition must describe the same solution.