Percentage Concentration to Molarity
Translate weight percent solutions into molarity for stoichiometry, reagent preparation, and analytical calculations.
Use 1.00 g/mL for water-like solutions.
Molarity
1.7967 mol/L
Grams per liter
105 g/L
Grams per 100 g solution
10 g
How to Use This Calculator
Find the percentage
Read the label or measure the weight percent (w/w) of solute in the solution.
Enter solution density
Use a known density or assume 1.00 g/mL for dilute aqueous solutions.
Provide molar mass
Look up the molar mass of the solute to convert grams to moles.
Review results
The tool reports molarity, grams per liter, and grams per 100 g of solution.
Formula
M = (w% × 10 × density) / Mᵣ
w% is weight percent (w/w), density is in g/mL, and Mᵣ is molar mass (g/mol). The factor of 10 converts 100 g to 1 L using density.
Example
For 10% NaCl with density 1.05 g/mL: M = (10 × 10 × 1.05) / 58.44 ≈ 1.80 mol/L.
Full Description
Percentage concentration (w/w) expresses how many grams of solute are present in 100 grams of solution. Molarity, however, is defined per liter of solution. Converting between the two requires solution density and molar mass.
This calculator automates the conversion, making it easier to translate manufacturing specifications or reagent labels into molarity for stoichiometry and analytical calculations.
Frequently Asked Questions
Can I use percent w/v instead?
w/v percent represents grams per 100 mL. Convert to grams per liter directly (multiply by 10) before dividing by molar mass.
What if density is unknown?
Assume 1.00 g/mL for dilute aqueous solutions. For concentrated solutions, obtain density from datasheets for better accuracy.
Does temperature matter?
Density and molarity are temperature-dependent. Use densities measured at the relevant temperature for precise results.
Can this handle mixtures of solutes?
The calculation assumes a single solute. For mixtures, convert each solute’s percentage separately if data is available.
Why does percent need to be under 100?
Weight percent is defined per 100 g of solution. Values ≥100% are physically impossible.