Alcohol Dilution Calculator

Calculate how much water (or diluent) to add to a high-strength alcohol solution to reach a desired lower concentration.

Initial Volume (mL)

Initial Concentration (% ABV)

Desired Final Concentration (% ABV)

Based on the conservation of solute principle:

C₁ × V₁ = C₂ × V₂

Solving for the final volume:

V₂ = (C₁ × V₁) / C₂

Water to add:

V_water = V₂ − V₁ = V₁ × (C₁/C₂ − 1)

Where C₁ = initial ABV (%), V₁ = initial volume (mL), C₂ = desired ABV (%), V₂ = final volume (mL).

Concentrations are expressed as % ABV (Alcohol By Volume) — the standard used in distilling and spirits production.
The diluent is assumed to be pure water (0% ABV).
The formula assumes ideal mixing. In practice, mixing ethanol and water produces a slight volume contraction (~2–3% at mid-range concentrations) due to hydrogen bonding. For high-precision distilling, use the OIML International Alcoholometric Tables or TTB gauging tables.
Temperature is assumed to be 20 °C (68 °F), the standard reference temperature for ABV measurement.
Reference: OIML R 22 — International Alcoholometric Tables; US TTB (Alcohol and Tobacco Tax and Trade Bureau) Gauging Manual.

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