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Mixing Solutions Calculator

Enter the volume and concentration of each solution to get the blended concentration.

How it is calculated

The final concentration is the volume-weighted average of the two solutions: C = (V1 × C1 + V2 × C2) ÷ (V1 + V2). V1 and V2 are the volumes (any one unit, used for both), C1 and C2 the starting concentrations in percent. The numerator is the total amount of solute, the denominator the total volume, which the tool assumes is simply V1 + V2. The result is labelled in percent and shown with two decimals, along with the total volume. A solution with concentration 0 acts as pure solvent, so this also covers dilution. If the total volume is zero or any field is empty, there is no result. Volumes of some liquids do not add exactly (for example alcohol and water), so a real mixture can differ slightly.

Worked example

Mix 200 mL of a 10% solution with 300 mL of a 25% solution. Solute from the first: 200 × 10 = 2000. Solute from the second: 300 × 25 = 7500. Total solute: 9500. Total volume: 200 + 300 = 500. Final concentration: 9500 ÷ 500 = 19.00%. It sits between 10% and 25%, closer to 25% because the stronger solution has the larger volume. Mixing 500 of a 70% solution with 500 of pure water (0%) gives 35.00%, exactly half.

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Common mistakes

  • Averaging the two concentrations without weighting by volume: (10 + 25) ÷ 2 = 17.5% is wrong when the volumes differ, the correct answer here is 19%.
  • Using different volume units for the two solutions, for example 200 mL with 0.3 L: the same unit must be used for both.
  • Mixing concentration types: the tool treats both values as the same kind of percent, so a w/v percent cannot be blended with a v/v percent or with a molarity.
  • Entering a dilution with water as its own concentration: pure solvent is concentration 0, not 100.
  • Expecting the total volume to be exact for liquids that contract on mixing: the tool just adds the two volumes.

About this calculator

When two solutions of different volumes and concentrations are combined, the total amount of solute is conserved even though the concentration changes — the principle behind the classic C1V1 + C2V2 = C3V3 mixing equation, where C3 is the final blended concentration and V3 is the sum of the two volumes. This is the same logic used in reverse for dilution (adding pure solvent, C2 = 0) and in alligation problems for blending two stock solutions to hit a target strength.

Chemists, pharmacists and lab technicians rely on this constantly — diluting a stock reagent to a working concentration, blending two batches of a solution with slightly different strengths, or preparing a solution of exact molarity from two available stocks.

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Comments (1)

  • Editorial team

    Before pressing calculate, you can bound the answer: the blend must land between the two starting strengths, pulled toward whichever solution has more volume. With 200 at 10% and 300 at 40%, the tool returns 28.00% for a total of 500.00, which is 60% of the way up because 300 is 60% of the volume. If your result falls outside the two inputs, recheck a typo. Which concentration basis do you work in: w/v, v/v or w/w?

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