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

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Molarity To Weight Percent Formula

The following formula is used to calculate the Molarity To Weight Percent. Use consistent units for molarity and volume (for example, mol/L with L, or mol/mL with mL). If your molarity is in mol/L and your volume is in mL, convert mL to L by dividing by 1000 (or use the unit dropdowns in the calculator above). 

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%