Solution Mixing Calculator

C(final) = Σ(Cᵢ × Vᵢ) / Σ Vᵢ

Work out the final concentration when two or more solutions of the same solute are combined.

Solutions to combine

Concentration

Volume

Concentration

Volume

Result

280 mM

140 mmol of solute in 500 mL.

Calculation

Amount from Solution A
n = c × V
n = 1 mol/L × 0.1 L
n = 0.1 mol
Amount from Solution B
n = c × V
n = 0.1 mol/L × 0.4 L
n = 0.04 mol
Total amount of substance
n(total) = Σ nᵢ
n(total) = 0.14 mol
Total volume
V(total) = Σ Vᵢ (volume additivity assumed)
V(total) = 0.5 L
Final concentration
C(final) = n(total) / V(total)
C = 0.14 mol / 0.5 L
C = 0.28 mol/L

Inputs

Solution A: 1 mol/L × 0.1 L
Solution B: 0.1 mol/L × 0.4 L

All solutions are assumed to contain the same solute; concentrations of different solutes cannot simply be added.

Volumes are assumed to be additive. Real mixtures — especially concentrated solutions, alcohols and acids — can contract or expand on mixing, so make up to a final volume in a volumetric flask when accuracy matters.

No density, molecular weight or reaction between the components is assumed.

Where the solute comes from

Solution A100 mL71.43%
Solution B400 mL28.57%

Final concentration280 mM

Total volume 500 mL, assuming the volumes are additive.

About this calculator

When solutions of the same solute are combined, the amount of solute each one contributes is added up and divided by the total volume. Every concentration is converted to mol/L (or g/L for mass concentrations) and every volume to litres before the sum, so units may be mixed freely between rows.

All entered concentrations must describe the same solute and the same kind of quantity. This calculator works in molar concentration; convert mass concentrations first with the molarity calculator, which asks for the molecular weight rather than assuming one.

Volumes are assumed to be additive. For concentrated solutions, mixed solvents or strongly exothermic combinations this assumption breaks down; prepare to a marked final volume instead of relying on the sum.

LabReadyTools is provided as a calculation aid. Users remain responsible for verifying calculations, units, chemical compatibility, experimental procedures and applicable safety requirements before laboratory use.