Molarity Calculator
Molarity calculator: find the concentration in mol/L from the mass of solute, molar mass and volume, or the mass needed for a solution.
c = mM · V
How to use this calculator
- Choose the quantity you want under “Solve for”.
- Type the known values and pick their units: any combination works.
- The result updates as you type. Open “Show the steps” to see the substitution.
Molarity (molar concentration) c is the amount of solute per liter of solution, in mol/L (M). With the mass of solute m, its molar mass M and the solution volume V, it is c = m/(M·V).
Use it to prepare solutions in the lab: set the target concentration and volume, and solve for the mass you need to weigh.
Formula
c = mM · V
| Symbol | Quantity | Units |
|---|---|---|
| m | Mass of solute | kg, g, mg, µg, t, lb, oz, st, US ton, ct, Da |
| M | Molar mass | g/mol, kg/mol |
| V | Solution volume | L, mL, µL, m³, dm³, cm³, gal, gal (UK), qt, pt, cup, fl oz, ft³, in³ |
| c | Molar concentration | mol/L, mmol/L, µmol/L, nmol/L, mol/m³ |
Worked example
Given: m = 5.844 g · M = 58.44 g/mol · V = 100 mL
c = mM · V
Result: c = 1 mol/L
Frequently asked questions
How many grams do I need for 250 mL of 0.5 M NaCl?
m = c · M · V = 0.5 mol/L × 58.44 g/mol × 0.250 L = 7.305 g.
What is the difference between molarity and molality?
Molarity is per liter of solution and changes slightly with temperature. Molality is per kilogram of solvent and does not.