Alcohol Dilution Calculator
Work out exactly how much water to add to hit your target ABV — for bartenders proofing down overproof spirits, home brewers/vintners adjusting a batch, and hobbyist bottlers.
The simple method assumes volumes add directly — what most calculators and recipe books use, accurate enough for most bottling jobs.
| Starting volume | 0 L |
| Current ABV | 0% |
| Target ABV | 0% |
| Pure alcohol content | 0 L |
| Water to add | 0 L |
| Final total volume | 0 L |
Estimate only. This tool is intended for cocktail/mixology use, home brewing & winemaking, and legally produced spirits — always follow your local laws regarding alcohol production and bottling. Not a substitute for a calibrated hydrometer or alcoholmeter when precision matters (e.g. commercial bottling for tax/label compliance).
Common bottling & serving strengths
Standard spirits
- Vodka — 40% ABV (80 proof)
- Gin — 40–47% ABV (80–94 proof)
- Rum — 40–50% ABV (80–100 proof)
- Whiskey — 40–50% ABV (80–100 proof)
Specialty strengths
- Cask strength — 55–65% ABV (110–130 proof)
- Navy strength — 57% ABV (114 proof)
- Liqueurs — 15–30% ABV (30–60 proof)
- Fortified wine — 17–22% ABV
Frequently asked questions
How is alcohol dilution calculated?
The core formula is: Water to add = Volume × ((Current ABV ÷ Target ABV) − 1). This finds how much water is needed so that the same amount of pure alcohol is now spread across a larger total volume at your target strength.
Why does the result change slightly with the "contraction-corrected" method?
When you mix alcohol and water, the resulting volume is very slightly less than the sum of the two volumes — molecules pack together more tightly than in either liquid alone. This is called volume contraction. It's a small effect (typically under 1-3% depending on strength), but the contraction-corrected method accounts for it, which matters more at higher precision or larger batch sizes.
Does temperature affect the result?
Yes. ABV/proof measurements are standardized at 20°C (68°F). If you measure or dilute at a different temperature, the true ABV will differ slightly from the reading on a hydrometer or alcoholmeter unless you apply a temperature correction table. For most home and bar use this difference is small enough to ignore, but it matters for precise commercial bottling.
Why do some spirits go cloudy when diluted?
This is called "louching" — it happens with spirits like absinthe, ouzo, and some gins that contain essential oils (anise, botanicals) which are soluble in high-proof alcohol but not in water. As the ABV drops during dilution, the oils come out of solution and scatter light, creating a cloudy or milky appearance. It's a normal, expected effect for these spirits, not a fault.
What's the right order — water into alcohol, or alcohol into water?
Add water to the spirit gradually while mixing gently, rather than the reverse. This gives you more control to monitor ABV as you go and avoids splashing with high-proof spirit. Let the mixture rest for a day or two afterward — the alcohol and water molecules take time to fully integrate, and ABV readings can shift slightly in the meantime.
Is this calculator legal to use for making moonshine?
This calculator is intended for legal uses — mixology and cocktail work, home brewing/winemaking, and diluting commercially or legally produced spirits. Home distillation of spirits is illegal without a license in many countries, including the US, UK, Australia, and Canada. Check your local laws before distilling anything at home.