Alcohol Dilution Calculator — Water Down Spirits to Target ABV
Use this free alcohol dilution calculator to find out exactly how much water to add to dilute any spirit from its current ABV to your desired target ABV. Based on the dilution formula C1V1 = C2V2. Supports mL/L volumes, % ABV, and US proof. Ideal for home distillers, whisky enthusiasts, and cocktail crafters.
Dilute Your Spirit
Enter the volume and ABV of your spirit and the target ABV. The calculator will tell you how much water to add using the dilution formula V1C1 = V2C2.
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Frequently Asked Questions
How do I calculate how much water to add to dilute a spirit?
Use the dilution formula C1V1 = C2V2. Multiply your starting volume by your starting ABV, then divide by your target ABV to get the final volume. The difference between the final volume and the starting volume is how much water to add. For example, to dilute 1 liter of 60% ABV whisky to 40%: final volume = (1000 mL × 60%) / 40% = 1500 mL, so you add 500 mL of water.
What is ABV and how does it differ from proof?
ABV (Alcohol By Volume) is the percentage of pure ethanol in a liquid by volume. US proof is simply twice the ABV — so 80-proof vodka is 40% ABV, and 100-proof bourbon is 50% ABV. The UK historically used a different proof scale (Sykes proof), but it has been replaced by ABV globally.
What type of water should I use to dilute spirits?
Always use distilled or reverse-osmosis (RO) water. Tap water contains chlorine, minerals, and dissolved solids that can react with aromatic compounds in the spirit, causing off-flavors, cloudiness, or haze. Distilled water is neutral and will not alter the flavor profile beyond the dilution effect.
Why does my spirit go cloudy when I add water?
Clouding (louching) happens when essential oils and aromatic compounds that were dissolved in high-ABV alcohol precipitate out as the alcohol concentration drops. This is common with anise spirits like absinthe, ouzo, and pastis, and can also occur with some gin and whisky at very high ABV. It is generally harmless. Adding water slowly and keeping both liquids at room temperature minimizes the effect.
Is the dilution formula perfectly accurate?
The C1V1=C2V2 formula is accurate for most practical purposes, but it does not account for volume contraction. When alcohol and water mix, the combined volume is slightly less than the sum of the two volumes due to hydrogen bonding between ethanol and water molecules. The contraction is typically 1–3% and is most significant at around 50% ABV. For commercial blending, use the OIML tables or Pearce Tables for precise calculations.
Can I use this calculator for wine or beer?
Yes, the math works for any water-based alcohol solution. However, diluting wine or beer is unusual because it significantly alters the character, flavor balance, and mouthfeel of the beverage. The calculator is most useful for distilled spirits — whisky, vodka, gin, rum, brandy, and grain alcohol — where dilution is a normal part of the blending and bottling process.
What is cask-strength whisky?
Cask-strength (also called barrel-proof or cask-proof) whisky is bottled directly from the barrel without dilution. It typically ranges from 55% to 68% ABV (110–136 proof), though some barrels can yield even higher concentrations. Many enthusiasts prefer to add their own water to taste, which is exactly what this dilution calculator is designed to help with.
How much does dilution affect flavor?
Dilution dramatically affects spirit flavor. Adding water reduces alcohol burn, which can open up aromatic compounds and make flavors more accessible. Many professional tasters dilute high-ABV spirits to 20–30% for nosing. For drinking, many whisky enthusiasts add just a few drops of water to 'open up' a dram. Conversely, too much water can make a spirit taste thin and flat, washing out delicate flavors.
About the Alcohol Dilution Calculator
Dilution Formula (C1V1 = C2V2)
Alcohol dilution is governed by the law of conservation of solute. The amount of pure alcohol in the solution before dilution must equal the amount after dilution. This gives us the classic dilution equation:
C1 × V1 = C2 × V2
V2 = (C1 × V1) / C2
Where:
- C1 — Initial concentration (current ABV as a percentage)
- V1 — Initial volume (your starting amount of spirit)
- C2 — Target concentration (desired ABV)
- V2 — Final volume after dilution
The water to add is simply V2 − V1.
Example: Dilute 1 L of 60% cask-strength whisky to 40% ABV
V2= (60% × 1 000 mL) / 40% = 1 500 mL
Water to add = 1 500 mL − 1 000 mL = 500 mL
Note on volume contraction:When alcohol and water mix, the total volume is slightly less than the sum of the two volumes due to molecular interactions. This effect is negligible for most hobby applications (typically <2%) but is significant in commercial distilling, where the Pearce Tables or OIML tables are used for precise blending.
Proof vs ABV
ABV (Alcohol By Volume) is the universal scientific measure of alcohol concentration, expressed as a percentage. A spirit labeled 40% ABV contains 40 mL of pure ethanol per 100 mL of liquid.
Proof is a historical measure still used primarily in the United States. US proof is exactly twice the ABV:
US Proof = ABV × 2
ABV = US Proof / 2
So 80-proof vodka is 40% ABV, and 190-proof Everclear is 95% ABV. The UK historically used a different proof scale (Sykes proof, where 100 proof = 57.1% ABV), but it has been phased out in favor of ABV.
| US Proof | ABV (%) | Example Spirit |
|---|---|---|
| 80-proof | 40% | Standard vodka, gin, rum, whiskey |
| 86-proof | 43% | Many bourbons and Scotch whiskies |
| 100-proof | 50% | Bottled-in-bond bourbon, overproof rum |
| 120-proof | 60% | Cask-strength whisky |
| 190-proof | 95% | Everclear grain alcohol |
Common Spirit ABVs
Use this table as a reference when you don't have the exact ABV of your spirit. Always check the label when available.
| Spirit | Typical ABV | US Proof | Notes |
|---|---|---|---|
| Beer (lager/ale) | 3.5–7% | 7–14-proof | Not suitable for dilution |
| Wine | 11–14% | 22–28-proof | Table wine range |
| Vodka | 37.5–50% | 75–100-proof | Standard 40% (80-proof) is most common |
| Gin | 37.5–50% | 75–100-proof | London Dry minimum 37.5% |
| Rum | 37.5–80% | 75–160-proof | Overproof rum can be very high ABV |
| Tequila / Mezcal | 35–55% | 70–110-proof | Minimum 35% for tequila |
| Whiskey / Bourbon | 40–68% | 80–136-proof | Cask strength can exceed 60% |
| Scotch Whisky | 40–65% | 80–130-proof | Minimum 40% ABV required |
| Brandy / Cognac | 35–60% | 70–120-proof | Most cognac is 40% ABV |
| Grain Alcohol (Everclear) | 75–95% | 150–190-proof | Widely used for tinctures and infusions |
Dilution Tips
- Use distilled water. Tap water contains chlorine, minerals, and other dissolved solids that can react with aromatic compounds in spirits, causing off-flavors, haze, or cloudiness. Distilled or reverse-osmosis water is the preferred choice for home distillers and blenders.
- Add water slowly. Especially at ABVs above 60%, adding water too quickly can cause temporary haze (louching) due to precipitation of essential oils. Add a small amount, stir gently, then continue. This is especially important with high-ABV gin, absinthe, and ouzo.
- Rest after dilution.After blending, allow the spirit to rest for at least 24–48 hours before evaluating flavor. The molecular interactions between ethanol and water take time to reach equilibrium, and the taste can change significantly during this period.
- Temperature matters. Both the spirit and the water should ideally be at room temperature before blending. Cold water added to warm alcohol can accelerate louching. Measure volumes at consistent temperature for accuracy.
- Account for volume contraction. When alcohol and water are mixed, the combined volume is slightly less than the sum of the individual volumes (up to ~3% at high ABV). For commercial production, use OIML tables or the Pearce Tables for precise calculations. For hobby use, this tool provides an excellent working approximation.
- Verify with a hydrometer. After dilution, verify the final ABV using a calibrated alcoholmeter or hydrometer. This is essential for ensuring accuracy and for any regulatory compliance.
Disclaimer
This calculator is provided for educational and hobbyist purposes only. It uses the simplified ideal dilution formula and does not account for volume contraction or temperature effects. Results should be verified with a calibrated instrument before use in commercial or regulatory contexts. Always comply with local laws regarding distillation and alcohol production.