Alcohol Dilution Calculator
Calculate how much water to add when diluting spirits from a current ABV to a lower target strength, with a US proof reference.
Must be lower than current ABV
Add Water
375 mL
Final Volume
1,125 mL
Pure Alcohol
450 mL
Calculation model
The calculator uses a pure-ethanol balance and reports an ideal volume before molecular contraction.
Precise proofing can require hydrometer readings, temperature correction and official gauging tables. US proof is twice the ABV percentage.
This calculator is not medical, legal or safety advice. It does not verify ingredient quality, product safety, labeling compliance, fire risk controls or local alcohol laws.
Dilute spirits by ABV or proof
English search intent for alcohol dilution is practical proofing: enter the current spirit volume, current ABV and a lower target ABV, then estimate how much water to add. US proof is included as a reference conversion, not as a separate input.
Vwater - water to add, V1 - starting volume, C1 - current ABV, Ctarget - target ABV.
proofUS - US proof value, ABV - alcohol by volume percentage.
Contraction and measurement limits
When ethanol and water mix, the final physical volume can be lower than the simple sum. The calculator shows an ideal balance before molecular contraction, which is enough for rough planning but not for regulated proofing.
| Need | Calculator result | What still needs checking |
|---|---|---|
| Kitchen or hobby planning | Water amount and ideal final volume | Flavor, rest time and measured ABV |
| US proof conversion | ABV times 2 | Hydrometer calibration and temperature |
| Labeling or regulated use | Not sufficient | TTB gauging rules and compliant instruments |
| Health or drinking decisions | Not sufficient | Medical advice and alcohol-use risk guidance |
Common dilution examples
| Starting spirit | Target | Water per 750 mL |
|---|---|---|
| 60% ABV cask strength | 40% ABV | 375 mL |
| 50% ABV bottled-in-bond | 40% ABV | 188 mL |
| 45% ABV spirit | 40% ABV | 94 mL |
| 95% ABV neutral spirit | 40% ABV | 1,031 mL |
Frequently Asked Questions
Sources and References
- Alcohol Dilution CalculatorCalcBee
- Gauging Manual for Distilled SpiritsTTB
- Alcohol Use and Your HealthCDC
- Dilution of SolutionsChemistry LibreTexts
Calculations are based on the listed reference sources. Links open in a new tab.
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