Alcohol Dilution Calculator
Enter your starting concentration and volume along with your target concentration to find the final volume and water needed.
How alcohol dilution is calculated
This calculator uses the dilution formula C1V1 = C2V2, rearranged to find your final volume: V2 = (C1 × V1) / C2. The water to add is simply the final volume minus your starting volume, since you're adding water rather than removing alcohol.
This formula works because the total amount of pure alcohol stays the same before and after dilution — only the total volume changes as water is added, which is why the concentration (a ratio) decreases proportionally.
Frequently asked questions
Does this work for any liquid dilution, not just alcohol?
Yes — the C1V1 = C2V2 formula applies to diluting any solution where you're adding a diluent (like water) to reduce a concentration, as long as you're not accounting for any volume change from mixing (which is usually negligible for simple dilutions).
Why does this calculator require the target concentration to be lower than the starting concentration?
You can only dilute downward by adding water — you can't increase concentration by adding more water. Reaching a higher target concentration would require removing water or adding more concentrated alcohol instead.
Is there a slight volume change when mixing alcohol and water?
Yes — mixing ethanol and water causes a slight volume contraction (the final volume is marginally less than the simple sum of the two volumes) due to molecular packing effects. This calculator uses the simplified additive model, which is accurate enough for most practical purposes.