Percentage Concentration to Molarity Calculator
Convert from weight percent, volume percent, or weight/volume percent to molarity. Enter solute molar mass and solution density.
Leave at 1.0 for dilute aqueous solutions
Needed for v/v% only
What is weight percent (w/w) concentration?
Weight percent (w/w) is the mass of solute per 100 grams of solution: w/w% = (mass of solute / mass of solution) × 100. A 10% w/w NaCl solution contains 10 g NaCl per 100 g total solution (90 g water). It's temperature-independent since mass doesn't change with temperature.
What is volume percent (v/v) concentration?
Volume percent (v/v) is the volume of solute per 100 mL of solution: v/v% = (volume of solute / volume of solution) × 100. Commonly used for liquids in liquids, like 70% isopropyl alcohol (70 mL alcohol per 100 mL solution). Temperature affects volume, so not ideal for precise work.
What is weight/volume percent (w/v)?
Weight/volume percent (w/v) is grams of solute per 100 mL of solution: w/v% = (mass of solute / volume of solution) × 100. A 5% w/v NaCl solution contains 5 g NaCl per 100 mL solution. Commonly used in biology and pharmacy. Note: It assumes solution density ~1 g/mL for dilute solutions.
How do I convert w/v% to molarity?
For w/v%: M = (w/v% × 10) / Molar Mass. Example: 5% w/v NaCl (M = 58.44 g/mol). M = (5 × 10) / 58.44 = 0.855 M. The factor 10 converts g/100mL to g/L, then dividing by molar mass gives mol/L.
What assumptions are made in these conversions?
The main assumption is solution density of 1 g/mL for w/v to w/w conversions. For dilute aqueous solutions, this is accurate. For concentrated solutions or non-aqueous solvents, you need the actual density. The conversion w/v% ≈ w/w% for dilute aqueous solutions.
Why do we need to convert between concentration units?
Different applications require different units. Molarity is essential for stoichiometry and reaction rates. Weight percent is used for solution preparation in labs (easy to weigh). Volume percent is common for commercial products (alcohol, hydrogen peroxide). Having multiple options allows flexibility in preparation methods.