Alcohol Dilution Calculator
Find out exactly how much water to add to dilute a spirit, liqueur, or any alcohol solution from a starting ABV to a lower target ABV. The result updates instantly as you change any input.
%
L
%
Final volume: 1.25 L at 40 % ABV
- 1
Final volume (V₂)
50 × 1 ÷ 40 = 1.25From C₁ × V₁ = C₂ × V₂, solved for V₂. - 2
Water to add
1.25 − 1 = 0.250
How does this calculator work?
Water to add = V₁ × (C₁/C₂ − 1). For example, diluting 1 L of 50 % ABV spirit to 40 % requires adding 0.25 L of water, giving a final volume of 1.25 L. The formula C₁V₁ = C₂V₂ conserves the amount of pure alcohol while increasing total volume. Enter starting ABV, volume, and target ABV to get the result.
Formula
How this is calculated
When you dilute an alcohol solution with water, the amount of pure alcohol stays the same — only the total volume (and therefore the concentration) changes. This is captured by the conservation equation C₁ × V₁ = C₂ × V₂, where C₁ and V₁ are the starting ABV and volume, and C₂ and V₂ are the target ABV and the required final volume. Rearranging gives V₂ = C₁ × V₁ / C₂, and the water to add is simply V₂ − V₁.
Example: you have 1 litre of 50 % ABV spirit and want to bring it to 40 %. V₂ = 50 × 1 / 40 = 1.25 L, so you need to add 0.25 L (250 mL) of water. The dilution factor is 1.25×.
The calculation assumes ideal mixing (C₁V₁ = C₂V₂). In reality, mixing ethanol and water releases a small amount of heat and causes a slight contraction — total volume can be up to ~3 % less than the sum of the parts near 50 % v/v. For craft spirits and cocktail work this approximation is more than sufficient; laboratory-grade dilutions for standards or analytical purposes may require the published Alcoholometric Tables (OIML R 022).
Frequently asked questions
Use C₁V₁ = C₂V₂. For example, to bring 1 L of 96 % ethanol to 40 %: V₂ = 96/40 × 1 = 2.4 L, so add 1.4 L of water. Always add spirit to water (not the reverse) to minimise heating and mixing hazards. Use cold water to reduce the slight volume contraction and let the mixture cool before measuring final volume.
Yes — alcohol density and volume both vary with temperature. The C₁V₁ = C₂V₂ formula applies to mass-based concentrations at the same temperature. For high-precision work, measure at 20 °C (the standard temperature for alcoholometry) and consult the OIML Alcoholometric Tables. For home distilling or cocktails, the formula is accurate enough at room temperature.
Yes — the C₁V₁ = C₂V₂ dilution formula applies to any solution where you are adding pure solvent (water) to reduce concentration. It is the same formula used in chemistry labs for diluting stock solutions of acids, bases, or dyes. Just interpret C as concentration in any consistent unit (%, g/L, mol/L).
TG we-Calculate Editorial Team. (2026). Alcohol Dilution Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/alcohol-dilution-calculator
TG we-Calculate Editorial Team. "Alcohol Dilution Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/alcohol-dilution-calculator.
TG we-Calculate Editorial Team, "Alcohol Dilution Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/alcohol-dilution-calculator
@misc{wecalculate_alcohol_dilution_calculator, title = {Alcohol Dilution Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/alcohol-dilution-calculator}}, year = {2026}, note = {TG we-Calculate} }
Did this calculator help you?