Alcohol Dilution Calculator (C₁V₁ = C₂V₂)
Dilute spirits & homebrew precisely: enter start ABV, target ABV and volume — get the exact water to add, final volume, and a what-if dilution table. ABV / US Proof toggle included. 100% client-side, no data leaves your device.
Legal & lawful use only. This tool is for legal homebrewing and spirit handling where permitted. Distilling spirits at home is illegal in many countries (including under US federal law without a permit). Always check your local laws.
Dilution calculator
WATER TO ADD
–
Final volume–
Final strength–
Pure alcohol (unchanged)–
What-if table: add water → resulting ABV
Water added as a share of your start volume (ideal-mixture approximation; real mixtures contract ~1–3%).
| Water added | Total volume | Result ABV | Result proof |
|---|
Worked examples (verified)
1. Whiskey 40% → 35%, 750 ml. V2 = 750 × 40/35 = 857.14 ml, so add 107.14 ml water. Final: 857.14 ml at 35% ABV (70 proof). Pure alcohol stays 300.00 ml.
2. Neutral spirit 60% → 40%, 500 ml. V2 = 500 × 60/40 = 750.00 ml, so add 250.00 ml water. Final: 750.00 ml at 40% ABV.
3. US: 80 proof → 70 proof, 1 gallon. 80 proof = 40% ABV, 70 proof = 35% ABV. Add 540.77 ml water (18.29 fl oz ≈ 0.14 gal). Final: 4326.18 ml = 1.14 gal at 70 proof.
4. Liqueur base 95% → 20%, 1 L. V2 = 1 × 95/20 = 4.75 L, so add 3.75 L water. Final: 4.75 L at 20% ABV (40 proof).
How it works
Dilution conserves alcohol: C₁V₁ = C₂V₂. With start ABV C₁, start volume V₁ and target ABV C₂, the final volume is V₂ = V₁ × C₁/C₂, and the water to add is V₂ − V₁. US proof is simply 2 × ABV.
Volume contraction (honest approximation): ethanol and water contract slightly when mixed — a real batch typically measures ~1–3% below the sum of the parts at high ABV. Like every dilution calculator, this tool uses the ideal (additive) approximation. In practice, measure the water you add rather than filling to a final-volume mark.
Scope boundary: this tool dilutes alcoholic beverages (spirits, liqueurs, homebrew). Computing a beer's ABV from gravity readings belongs to beer-abv-calculator; laboratory cell concentrations belong to cell-dilution; general chemistry percent solutions belong to percent-solution.
Frequently asked questions
What formula does the alcohol dilution calculator use?
C1 × V1 = C2 × V2. C1 is the starting ABV, V1 the starting volume, C2 the target ABV, and V2 the final volume. The calculator solves for V2 = V1 × C1 / C2, and the water to add is V2 − V1. No alcohol is added or removed, so the amount of pure alcohol (C1 × V1) stays exactly the same.
Are volumes additive when diluting alcohol with water?
Not exactly. Ethanol-water mixtures contract slightly on mixing — a real mixture typically measures about 1–3% less than the sum of the two volumes at high ABV. This calculator uses the ideal-mixture (additive) approximation, which is standard for dilution calculators. For practical use, measure the water you ADD (107.14 ml in the worked example) rather than trusting the final volume mark exactly.
What is the difference between ABV and proof?
In the United States, proof is simply twice the ABV: 80 proof = 40% ABV, 100 proof = 50% ABV. The calculator's Proof toggle converts automatically (proof ÷ 2 = ABV). Note: the UK historically used a different proof scale, so this tool uses US proof only.
Why does it show an error when the target ABV is higher than the start?
Dilution can only lower the strength. If the target ABV is equal to or higher than the starting ABV, there is nothing to dilute — reaching a higher ABV requires concentration (such as distillation) or blending with a stronger spirit, which is outside this calculator's scope.
Why is a target ABV of 0% rejected?
A target of 0% means pure water, not a diluted spirit — C1V1=C2V2 breaks down because the final volume would be infinite. Enter a small positive target (for example 1%) if you want a very weak mixture.
Does diluting change the total amount of alcohol?
No. Dilution only adds water, so the total pure alcohol stays constant: 750 ml at 40% ABV contains 300 ml of pure alcohol, and after adding 107.14 ml of water you still have 300 ml of alcohol in 857.14 ml at 35% ABV.
Can I use this for homebrewing or diluting a finished beer or wine?
Yes, for simple ABV reduction of any alcoholic liquid — spirits, liqueurs, high-ABV homebrew batches. If instead you want to compute a beer's ABV from gravity readings, use our beer ABV calculator; for laboratory cell concentrations, our cell dilution tool handles those.
Is it legal to dilute spirits or distill at home?
Diluting a legally purchased spirit is generally fine, but distilling spirits at home is illegal in many countries — including under US federal law without a permit — and homebrewing rules vary by region. This tool is for lawful, legal use only (for example adjusting a legally made liqueur or planning a homebrew dilution where permitted). Always check your local laws.
Free tool by NRTechStudio