LabReadyTools

Solution Mixing Calculator

C(final) = Σ(Cᵢ × Vᵢ) / Σ Vᵢ

Mix two solutions and calculate the resulting concentration, total volume and amount of solute.

Solutions to combine

Solution A

Solution B

Results update as you type, once at least two solutions have a concentration and a volume.

Result

280 mM

140 mmol of solute in 500 mL.

Calculation

  1. Amount from Solution A

    n = c × V

    n = 1 mol/L × 0.1 L

    n = 0.1 mol

  2. Amount from Solution B

    n = c × V

    n = 0.1 mol/L × 0.4 L

    n = 0.04 mol

  3. Total amount of substance

    n(total) = Σ nᵢ

    n(total) = 0.14 mol

  4. Total volume

    V(total) = Σ Vᵢ (volume additivity assumed)

    V(total) = 0.5 L

  5. 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.

Final solution

Final concentration
280 mM
Total volume
500 mL
Total solute
140 mmol

Volumes are assumed to be additive.

Mixing overview

  1. Solution A

    1 M

    100 mL

  2. Solution B

    100 mM

    400 mL

  3. Final solution

    280 mM

    500 mL

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

How to calculate concentration when mixing solutions

Each solution contributes an amount of solute equal to its concentration times its volume. Add those amounts, then divide by the combined volume:

C(final) = (C₁V₁ + C₂V₂) / (V₁ + V₂)

Worked example

Mixing 100 mL of 1 mol/L NaCl with 400 mL of 0.1 mol/L NaCl gives 0.100 mol + 0.040 mol = 0.140 mol of solute in 500 mL, so the final concentration is 0.140 mol / 0.500 L = 0.28 mol/L.

Mixing solutions with the same solute

This calculation only holds when every solution contains the same solute. Amounts of different solutes cannot be summed into one concentration — treat each solute separately and run the calculation once per solute.

Mixing solutions with different concentrations

Units may differ between rows: each concentration is converted to mol/L and each volume to litres before the amounts are added, so a stock in mmol/L can be combined with one in mol/L without converting by hand.

What happens to concentration after mixing?

The result always lies between the highest and the lowest starting concentration, weighted by volume — the larger volume pulls the mixture towards its own concentration. Volumes are assumed additive; concentrated acids, alcohols and strongly exothermic mixtures contract or expand, so make up to a marked final volume when accuracy matters.

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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.

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