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Alcohol Dilution Calculator – Online Proofing Down

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Dilution Inputs
%
150 Proof (US)
%
80 Proof (US)
Target must be lower than initial concentration.
Quick Presets:
Dilution Result
Water to Add
437.5
ml
Final Total Volume 1,187.5 ml
Pure Alcohol Content 281.3 ml
Dilution Ratio (water : original) 0.58 : 1
Final ABV / Proof 40.0% / 80 Proof
Original Solution
75% Alc
25% Water
After Dilution
40% Alc
60% Water
For every 100 ml of original spirit, add 58.3 ml of water.

Enter your values on the left to see the dilution result.

Frequently Asked Questions

Alcohol dilution is the process of adding water to a high-proof spirit to reduce its alcohol by volume (ABV) to a desired lower concentration. It's commonly used by distillers to bring raw distillate (often 70–95% ABV) down to bottling strength (typically 40–50% ABV), by home enthusiasts making liqueurs, and in laboratories preparing standard solutions. Proper dilution ensures the final product is safe, palatable, and meets legal or recipe specifications.

The standard dilution formula is C₁ × V₁ = C₂ × V₂, where C₁ is the initial concentration, V₁ is the initial volume, C₂ is the target concentration, and V₂ is the final volume after dilution. Rearranged: V₂ = (C₁ × V₁) / C₂. The amount of water to add is V₂ − V₁. For example, to dilute 750 ml of 75% ABV spirit to 40% ABV: V₂ = (75 × 750) / 40 = 1,406.25 ml, so add 656.25 ml of water. Note that this formula assumes ideal mixing; in reality, alcohol-water mixtures can exhibit slight volume contraction.

ABV (Alcohol By Volume) is the percentage of pure ethanol in a solution at 20°C (68°F), used internationally. Proof varies by system: In the United States, Proof = 2 × ABV (so 40% ABV = 80 Proof). In the UK (historical system), Proof ≈ ABV × 1.75, though the UK now primarily uses ABV like the rest of Europe. This calculator displays US Proof values for reference alongside ABV percentages.

For best results, use distilled or demineralized water. Tap water contains minerals, chlorine, and other impurities that can react with the alcohol, cause cloudiness (louching), or introduce off-flavors. Many commercial distilleries use reverse osmosis (RO) water. If you're making spirits at home, bottled spring water with low mineral content is also a good choice. Avoid using hard water, as calcium and magnesium can create haze in the final product.

Yes—alcohol hydrometers and density meters are calibrated for 20°C (68°F). At warmer temperatures, alcohol expands and becomes less dense, causing hydrometers to read lower than the actual ABV. At colder temperatures, the liquid contracts and readings appear higher. For precise work, measure the temperature of your spirit and use a temperature correction table or calculator. As a rule of thumb, a 5°C deviation can shift the ABV reading by approximately 1–1.5%.

Cloudiness (louching) occurs when certain compounds—especially fusel oils and fatty acid esters—become insoluble as the alcohol concentration drops. These compounds are soluble in high-proof alcohol but precipitate out when water is added. This is common with grain-based spirits and is actually a sign of a flavorful, non-chill-filtered product. To minimize cloudiness: use distilled water, add water slowly while stirring, and consider chill-filtering if clarity is essential. Some cloudiness in craft spirits is perfectly normal and harmless.

Absolutely! This calculator is designed for home distillers, cocktail enthusiasts, and anyone needing to proof down spirits. Common home uses include: diluting high-proof Everclear (95% ABV) to make homemade liqueurs and extracts; adjusting overproof rum or whiskey to a comfortable sipping strength; and preparing standardized alcohol solutions for tinctures. Always measure carefully, use clean equipment, and add water gradually while tasting (for consumable products).

When ethanol and water mix, the resulting total volume is slightly less than the sum of the individual volumes due to hydrogen bonding between molecules. For example, mixing 50 ml of pure ethanol with 50 ml of water yields approximately 96 ml of solution (about 4% contraction). For most practical dilution work—home distilling, cocktail making, and general lab use—the standard C₁V₁=C₂V₂ formula (which ignores contraction) provides sufficiently accurate results. Only in high-precision analytical chemistry or pharmaceutical applications is a contraction correction necessary.
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