Molarity Calculator
Choose what you want to find. Enter a formula and the molar mass fills in by itself.
- moles = M × V = 0.1 mol/L × 0.25 L = 0.025 mol
- mass = moles × molar mass = 0.025 × 58.443 g/mol = 1.4611 g
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Common lab solutions
| Solution | Formula | Molar mass | For 1 L of 1 M | For 100 mL of 0.1 M |
|---|---|---|---|---|
| Sodium chloride | NaCl | 58.44 | 58.44 g | 0.584 g |
| Sodium hydroxide | NaOH | 40.00 | 40.00 g | 0.400 g |
| Potassium chloride | KCl | 74.55 | 74.55 g | 0.746 g |
| Glucose | C6H12O6 | 180.16 | 180.16 g | 1.802 g |
| Copper(II) sulfate pentahydrate | CuSO4·5H2O | 249.68 | 249.68 g | 2.497 g |
| Tris base | C4H11NO3 | 121.14 | 121.14 g | 1.211 g |
| EDTA disodium dihydrate | C10H14N2Na2O8·2H2O | 372.24 | 372.24 g | 3.722 g |
Molarity in three lines
M = n ÷ V, where n is moles of solute and V is litres of solution (not solvent). Rearranged: n = M × V and V = n ÷ M. Every molarity problem is one of these, plus a grams-to-moles step using the molar mass.
Common slip: volume must be in litres. 250 mL is 0.250 L. The unit menus above convert for you.
From stock to working solution
If you already have a concentrated stock and need to water it down, that is a dilution problem, C₁V₁ = C₂V₂. Use the dilution calculator.
Questions students ask
What is the molarity formula?
Molarity M = moles of solute ÷ litres of solution. In mass terms, M = mass (g) ÷ (molar mass (g/mol) × volume (L)). The unit is mol/L, written M.
How do I make a solution of a given molarity?
Multiply molarity × volume (L) × molar mass to get the grams of solute. For 250 mL of 0.1 M NaCl: 0.1 × 0.250 × 58.44 = 1.461 g. Dissolve it in less water than you need, then top up to the 250 mL mark in a volumetric flask.
Is molarity the same as molality?
No. Molarity divides by litres of solution; molality divides by kilograms of solvent (mol/kg). Molality does not change with temperature, which is why it is used for boiling-point and freezing-point calculations.
How do I convert mg/mL or g/L to molarity?
Convert to g/L (1 mg/mL = 1 g/L), then divide by the molar mass. 9 g/L NaCl ÷ 58.44 g/mol = 0.154 M, the concentration of normal saline.
How do I convert percent (w/v) to molarity?
A w/v percentage is grams per 100 mL. Multiply by 10 to get g/L, then divide by the molar mass. 5% w/v glucose = 50 g/L ÷ 180.16 g/mol = 0.278 M.
What is the difference between molarity and normality?
Normality counts reactive equivalents per litre. For an acid it is molarity × number of H⁺ released: 1 M H₂SO₄ is 2 N. Normality depends on the reaction, which is why IUPAC discourages it.
How do I convert molarity to mg/mL?
Multiply molarity (mol/L) by molar mass (g/mol) to get g/L, which equals mg/mL. 0.1 M NaCl × 58.44 = 5.844 g/L = 5.844 mg/mL.