By Regina Edwards, Updated Mar 24, 2022
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A dilution solution is a mixture of a concentrated “stock” substance and a neutralizing “diluent.” The ratio of the two determines the final concentration. For instance, a 1:10 dilution means that 10 mL of the final mixture contains 1 mL of stock and 9 mL of diluent. The following method shows how to calculate the exact volumes needed for any dilution factor. This approach follows standard laboratory practice widely used in academic and industrial settings.
Decide how much total solution you need. For example, 30 mL.
Write the ratio as a proportion, such as 1:20 (one part stock to twenty parts total).
Express the ratio as a fraction: 1 ÷ 20 = 1/20.
Multiply the desired final volume by the fraction: 30 mL × 1/20 = 1.5 mL of stock.
Subtract the stock volume from the total: 30 mL – 1.5 mL = 28.5 mL of diluent.
Using a graduated cylinder, draw 1.5 mL of the stock solution into a clean container.
Measure 28.5 mL of the diluent (e.g., water or solvent) and add it to the same container.
Stir the combined solution with a glass rod until homogenous. Your 1:20 dilution is ready.
Accurate dilution calculations are essential for reproducible experiments and reliable data.
