Alcohol Dilution Calculator

How Alcohol Dilution Works

To reach a target ABV, mix a strong spirit with water or a weaker alcohol. The cross method compares concentrations:

$$\text{weaker volume} = \frac{(A - C) \times V}{C - B}$$

where $A$ is strong ABV, $B$ is weaker ABV, $C$ is target ABV, and $V$ is the strong volume. Pair with the Homebrew ABV Calculator when measuring fermentation strength from gravity readings.

Example

Dilute 1000 mL of 91% isopropyl alcohol to 70% with water (0% ABV). You need $(91 - 70) \times 1000 / 70 \approx 300$ mL of water for about 1300 mL total.

Volume Contraction

Mixed alcohol and water occupy slightly less volume than the sum of the parts. The optional contraction estimate uses common reference losses by target ABV.