How this calculator works
Conserve solute while mixing a higher and lower concentration. Every concentration must use the same amount-per-volume basis. For mass percentages, use this method with mass amounts instead or first convert using density. Volumes are assumed additive with no reaction. A target equal to one stock requires only that stock. A target outside the stock range cannot be made by mixing the two.
Formula
Ch Vh + Cl Vl = Ct (Vh + Vl). Vh/Vtotal = (Ct - Cl)/(Ch - Cl).
Worked example
Mixing 500 mL of an 80% stock with 500 mL of a 20% stock gives 1 L at 50%. To make 4 L at 25% from 100% and 0% stocks, use 1 L and 3 L.
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Frequently asked questions
Is this the same as dilution?
Dilution is the special case where the lower stock concentration is zero.
Can I mix two equal concentrations?
They do not define a unique ratio for a new concentration, so this tool requires different stocks.
Why might measured volume differ?
Some liquids contract or expand on mixing. Use a suitable density or measured final volume for precision.