Mixture of Two Solutions Calculator
Mix two solutions of different strengths and get the volume and concentration of the blend — the classic mixture word problem, solved.
How it works
Final % = (vA·cA + vB·cB) ÷ (vA + vB) · Solute = (vA·cA + vB·cB) ÷ 100
The strength of a blend is the weighted average of the two strengths, weighted by how much of each you pour in. Because it is a weighted average, the result always lands between the two starting concentrations — never above the stronger one or below the weaker one. The larger volume pulls the mixture toward its own concentration, which is why a small splash of a strong solution barely moves a large weak one.
Worked example
Mix 10 mL of a 20% solution with 30 mL of a 50% solution. The solute is (10·20 + 30·50) ÷ 100 = (200 + 1500) ÷ 100 = 17 mL, in a total of 40 mL, so the blend is 1700 ÷ 40 = 42.5% — closer to 50% because there is more of the strong solution.
Frequently asked questions
Why is the result not just the average of the two percentages?
A plain average would only be right if you used equal volumes. When the volumes differ, each concentration is weighted by its volume, so the larger portion pulls the result toward its own strength.
Can the final concentration be higher than both starting solutions?
No. A mixture is a weighted average, so its concentration always falls between the weaker and stronger solution. To go higher you would have to add pure solute, not another solution.
Does this work for salt, alcohol or acid solutions?
Yes, as long as both concentrations are measured the same way (percent by volume, or percent by mass) and the volumes add without shrinking. For alcohol–water, volumes contract slightly, so treat the result as a close estimate.
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This calculator is for educational purposes. Double-check important results before acting on them.