Calculator
Choose the value to calculate, then enter the other two values. M = n / V.
Formula and assumptions
M = n / V
Molarity is the amount of solute divided by the volume of the final solution. This calculator uses litres for volume and mol for amount of solute.
Assumption: The entered volume is the final solution volume.
Variables and units
Worked example
For 0.50 mol of solute in 0.50 L of solution, M = 0.50 / 0.50 = 1.00 mol/L.
Grams needed for common solutions
| Solute | Formula | Molar mass (g/mol) | Mass for 250 mL of 0.5 M |
|---|---|---|---|
| Sodium chloride | NaCl | 58.44 | 7.31 g |
| Potassium chloride | KCl | 74.55 | 9.32 g |
| Sodium hydroxide | NaOH | 40 | 5 g |
| Glucose | C₆H₁₂O₆ | 180.16 | 22.52 g |
| Copper(II) sulfate pentahydrate | CuSO₄·5H₂O | 249.69 | 31.21 g |
Mass = molarity × volume (L) × molar mass. Dissolve the solid in less than the final volume, then make up to the mark in a volumetric flask: adding 250 mL of water to the solid gives a slightly larger volume and a lower concentration. For hydrates such as copper sulfate pentahydrate, use the molar mass of the hydrate you weigh, including the water.
Important limits
This ideal calculation does not correct concentration for activity, temperature or volume change on mixing.
Reference and related tools
IUPAC: amount concentration. Return to Chemistry Calculators for the other tools in this group.