πΈ Alcohol Dilution Calculator
Dilute any spirit to your target ABV with C1V1 = C2V2. Exact water amounts.
Dilution Result
How to Dilute Alcohol to a Target ABV
The formula is C1V1 = C2V2: starting ABV times starting volume, divided by target ABV, equals the final volume. The difference between final and starting volume is the water to add. Enter your spirit's ABV, your target, and the starting milliliters; the calculator returns the water amount, final volume, and both proofs.
Enter the starting ABV (80-proof vodka is 40%) and your target ABV.
Enter the starting volume in milliliters. A fifth is 750 ml.
Add the calculated distilled water to the spirit, not the reverse, and stir gently.
Let it rest a few hours or overnight; freshly diluted spirit tastes harsh at first.
The Dilution Formula
Seven hundred fifty milliliters of 40% vodka to 20%: final = (40 Γ 750) Γ· 20 = 1,500 ml, so add 750 ml of water. The result is 1.5 liters at 20% ABV, or 40 proof. The target must be lower than the starting ABV; you cannot concentrate by adding water.
Worked Example: Vodka to Liqueur Strength
Enter 40% starting, 20% target, 750 ml. The calculator returns 750 ml of water to add and a 1,500 ml final volume at 20% ABV (40 proof). Pour the water into the vodka gradually, stirring; the mixture warms slightly as they combine, which is normal. Taste after resting: at 20% the vodka's heat is gone and any added flavoring (fruit, herbs) comes forward cleanly.
Why Dilution Changes Flavor
Water does more than lower the burn: it changes which aromatic compounds stay dissolved. High-proof spirit holds onto oily, heavy flavors; adding water releases volatile aromatics into the air above the glass, which is why a splash "opens up" whiskey. This is also why distillers proof down gradually and rest the spirit: the flavor equilibrium shifts with every addition. Dilute in steps and taste as you go rather than jumping straight to the target.
Practical Tips for Clean Dilution
Use distilled or demineralized water; tap water can cloud spirits and add chlorine notes. Chill both liquids first for the smoothest blend. Add water to the spirit in stages for large dilutions, tasting at each step. Label the final bottle with the new ABV and the date; diluted spirits keep like the original but the label prevents confusion. And keep high-proof stock locked away from kids: it looks like water.
Proofing down in stages gives the smoothest result for large dilutions. Dropping from 95% to 40% in one step can taste harsh for days; stepping through 70% then 55% then 40%, resting a day between, integrates the flavors. Commercial distillers rest diluted spirit for weeks before bottling for exactly this reason. Patience is an ingredient.
Dilution for Cocktails and Homemade Liqueurs
The same C1V1=C2V2 math powers homemade liqueurs. Infuse 750 ml of 100-proof vodka (50%) with fruit or herbs, strain, then dilute to 40 proof (20%) for a sipping liqueur: final volume = (50 Γ 750) Γ· 20 = 1,875 ml, so add 1,125 ml of simple syrup and water combined. Most liqueur recipes add the sweetener as the diluent: a 1:1 simple syrup both sweetens and dilutes in one step.
For cocktails, dilution happens in the glass: shaking with ice adds about 1 ounce of water to a 3-ounce drink, dropping a 30% ABV cocktail to about 22%. Stirred drinks dilute less, around 20%. Bartenders count on this: an undiluted Manhattan would be harsh, and the melt is part of the recipe. When batching cocktails for parties, add 20 to 25% water to the batch to replicate the shake.
Temperature correction is the professional's footnote. Hydrometers are calibrated at 60Β°F (or 20Β°C); spirit measured at 80Β°F reads about 2 proof low, at 40Β°F about 2 proof high. For legal labeling, distillers apply temperature correction tables. Home users can ignore it for liqueurs but should know it exists: if your diluted spirit tastes stronger than the math says, warm spirit is the likely explanation, not bad arithmetic.
Label every diluted bottle with the final proof and the date. Six months later you will not remember whether that jar is 80 proof or 60, and the label saves you from re-measuring.
Common Mistakes to Avoid
Using tap or mineral water is the flavor-killer; minerals defeat the purpose. Adding the spirit to the water instead of water to the spirit makes mixing harder for large batches. Judging the result immediately is second; fresh dilutions taste hot and need hours to settle. The dangerous mistake is confusing isopropyl with ethanol: dilution math is identical, but isopropyl is never for drinking, at any strength.
A Second Worked Example: High-Proof to Sipping Strength
Seven hundred fifty milliliters of 95% neutral spirit down to 40%. Final volume: 95 times 750 divided by 40 is 1,781 ml. Water to add: 1,781 minus 750 is 1,031 ml. That is more water than spirit, which surprises first-timers: proofing down is mostly adding water. Add it in stages, a third at a time, stirring gently and resting between additions. The mixture warms as water and alcohol combine, and rushing it makes for a harsher result.
At 95% the spirit is near-azeotropic and unforgiving; measure carefully, because small errors in the starting volume swing the final ABV noticeably. And keep it away from open flame during the whole process. High-proof spirit is seriously flammable, which the safety sheets say plainly and experience confirms.
Proofing Down Whiskey: The Distiller's Method
Distillers rarely proof down in one jump. They add water gradually over hours or days, letting the spirit rest between additions, because sudden dilution can shock the spirit into harshness that takes weeks to mellow. The resting matters as much as the math: freshly diluted whiskey tastes hot and disjointed, and the same bottle a week later tastes integrated.
Water choice matters more here than in cocktails. Distillers use demineralized or their own spring water; minerals in hard tap water can cloud the spirit and add off flavors. At home, distilled water is the safe default. And the target matters: most whiskeys land at 40-45% ABV not by accident but because that range balances flavor intensity against drinkability. Proof lower and the whiskey thins; bottle higher and it needs water in the glass anyway.
Common Dilution Mistakes
First: tap water. Chlorine and minerals in tap water can haze the spirit and add flavors you did not invite. Distilled water is cheap and neutral. Second: adding spirit to water instead of water to spirit. The convention exists for control: adding water gradually to the spirit lets you taste and stop. Third: no rest. Freshly diluted spirit always tastes harsher than it will in a week; judging it immediately leads to over-correction.
Fourth: diluting past the target with no way back. You cannot un-add water, so approach the target in small additions at the end and measure. Fifth: ignoring temperature. Volumes shift with temperature, and ABV is defined at a standard temperature (20C / 68F in the US system). For casual cocktail work this is trivia; for precise proofing, measure at room temperature and be consistent.
The Water You Use Matters More Than the Math
The dilution formula is exact, but the water is not neutral. Tap water carries chlorine, chloramine, and minerals that show up in the finished spirit as off flavors, especially at the low end where water is half the bottle. Distillers proofing whiskey down use demineralized or reverse-osmosis water for exactly this reason. At home, filtered water is the minimum; distilled water is better and costs almost nothing at the volumes we are talking about. One more detail people skip: add the water to the alcohol slowly, in stages, and let the blend rest a day or two before judging it. Freshly diluted spirit tastes hotter than the same bottle will taste after 48 hours, because the water and ethanol need time to fully integrate. Measure twice, pour slowly, and taste on day three.
Frequently Asked Questions
How do you dilute alcohol to a lower ABV?
Use C1V1 = C2V2: multiply your starting ABV by your starting volume, divide by the target ABV, and the result is the final volume. Add water to reach it. Example: 500 ml of 40% vodka to 20% gives 500 Γ 40 Γ· 20 = 1,000 ml final, so add 500 ml of water. Use distilled water for the cleanest taste.
How much water do I add to vodka to make it 20%?
Equal parts: 1 liter of 40% vodka plus 1 liter of water makes 2 liters at 20%. The math: 1,000 Γ 40 Γ· 20 = 2,000 ml final volume, so the added water is 1,000 ml. Chill both first and mix gently; the dilution warms slightly as the liquids combine.
What is the difference between ABV and proof?
In the US, proof is exactly twice the ABV: 80 proof means 40% ABV. The UK historically used a different proof scale, but modern labels worldwide use ABV. This calculator shows both. When a recipe says "dilute to 80 proof," it means 40% ABV.
Can you dilute whiskey with water?
Yes, and most drinkers should: a splash of water opens up whiskey's aroma by releasing volatile compounds. Master distillers dilute barrel-strength whiskey (often 55 to 65% ABV) down to bottling strength (40 to 46%) with water as standard practice. Add water gradually and taste; the sweet spot for most whiskeys is 40 to 45% ABV.
Does adding water to alcohol change the volume exactly?
Almost, but not perfectly: alcohol and water contract slightly when mixed, so 500 ml + 500 ml yields a touch under 1,000 ml (about 2 to 3% less). For home diluting this is negligible. Commercial distillers account for the contraction with precise tables; home users can ignore it.
What water is best for diluting spirits?
Distilled or demineralized water: it adds nothing, which is the point. Tap water's chlorine and minerals can cloud the spirit and add off flavors, especially in delicate vodka. If you must use tap water, filter it first. Never use mineral water; the minerals defeat the purpose.
How do you make 70% alcohol from 99% isopropyl?
The same C1V1 = C2V2 math: for 1 liter at 70% from 99%, final volume = 1,000 Γ 99 Γ· 70 = 1,414 ml, so add 414 ml of distilled water. Note that 70% isopropyl is actually the better disinfectant than 99%: the water helps it penetrate cell walls. This is for surfaces, never for drinking.
Can I dilute Everclear to vodka strength?
Yes: Everclear at 95% ABV (190 proof) dilutes to 40% vodka strength with the formula. One liter becomes 1,000 Γ 95 Γ· 40 = 2,375 ml final, adding 1,375 ml of water. Use distilled water, mix well, and let it rest a day; freshly diluted high-proof spirit tastes harsh until it settles. Check local laws on high-proof spirits first.
Why do distillers dilute whiskey before bottling?
Barrel-strength whiskey at 55 to 65% ABV is intense for most drinkers, and diluting to 40 to 46% makes it approachable while keeping flavor. Water also changes which flavor compounds stay dissolved, which is why the same whiskey tastes different at different strengths. Cask-strength bottlings skip this for enthusiasts who dilute in the glass.
Is it safe to drink diluted rubbing alcohol?
No, never. Isopropyl alcohol is toxic to drink at any dilution and can cause blindness, organ failure, and death. Dilution calculators for isopropyl are for making surface disinfectants only. Only ethanol (drinking alcohol) is safe for consumption, and even then in moderation.