Convert molarity and weight percent using molar mass and solution density, reverse-solve either concentration, and see batch solute, solvent, and sensitivity details.

Use the actual solution density at the relevant temperature and molar mass for the exact solute. Mass percent is grams of solute per 100 g of total solution. This model does not establish solubility or preparation safety.

Molarity To Weight Percent Formula

The following formula calculates weight percent from solute mass and total solution mass. Use matching molarity and volume units. Equivalently, WP = M × MW / (10ρ), where M is mol/L, MW is g/mol and ρ is solution density in g/mL. The calculator above uses this density form; batch volume scales the displayed masses.

WP = (M × V × MW / TM) × 100

Variables:

  • WP is the weight percent (%, w/w)
  • M is the molarity (for example, mol/L)
  • V is the total volume of solution (in the matching volume unit for M; for example, L if M is in mol/L)
  • MW is the molar mass (g/mol)
  • TM is the total mass of the entire solution (g)
Molarity to Weight Percent Conversion Table (NaCl in water, MW = 58.44 g/mol; ρ ≈ 1.00 g/mL; basis: 1 L solution)
Molarity (mol/L) Weight Percent (%)
0.010.058
0.020.117
0.050.292
0.100.584
0.201.169
0.251.461
0.301.753
0.502.922
0.754.383
1.005.844
1.257.305
1.508.766
1.7510.227
2.0011.688
2.2513.149
2.5014.610
2.7516.071
3.0017.532
4.0023.376
5.0029.220
*Assumes sodium chloride (MW 58.44 g/mol), solution density ≈ 1.00 g/mL, and a 1 L basis. Approximation: wt% ≈ M × MW / 10. Actual wt% varies with solution density.

How to Calculate Molarity To Weight Percent?

The following steps outline how to calculate the Molarity To Weight Percent.

  1. First, determine the molarity (typically mol/L).
  2. Next, determine the total volume of the solution (typically L). 
  3. Next, determine the molar mass (g/mol). 
  4. Next, determine the mass of the entire solution (g).
  5. Next, gather the formula from above: WP = (M*V*MW / TM) * 100. (Be sure M and V use matching volume units, e.g., mol/L with L.)
  6. Finally, calculate the Molarity To Weight Percent.
  7. 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.

molarity (mol/L) = 1

total volume of solution (L) = 1

molar mass (g/mol) = 30

total mass of solution (g) = 1,000

WP = (M*V*MW / TM) * 100 = (1*1*30 / 1000) * 100 = 3%