This alcohol dilution calculator answers the liqueur-maker’s question: given a spirit at one strength, how much water brings it to a target ABV? It uses the conservation of alcohol — C₁V₁ = C₂V₂ — and tells you the water to add and the final volume.

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C₁V₁ = C₂V₂, and One Physical Wrinkle

Dilution arithmetic is bookkeeping: the pure alcohol you start with is the pure alcohol you end with, so final volume = V₁ × C₁/C₂. The defaults tame a bottle of 95% neutral spirit (the Everclear-class base of homemade limoncello and tinctures): 750 mL × 95/40 → final 1,781 mL, meaning add ≈ 1,031 mL of water to land at vodka strength — two bottles’ worth of finished spirit from one, which is the entire economics of the liqueur shelf. The wrinkle is real physics politely flagged in the result: ethanol and water contract on mixing (hydrogen bonding packs them tighter), losing up to ~3.5% of the summed volume around equal-parts mixtures. Distillers therefore dilute by MEASUREMENT, not just arithmetic — gauging tables (the TTB’s official tables exist precisely for this) or a proof hydrometer reading after mixing, trimming with small water additions to the legal bottling strength. The calculator’s number is the correct starting dose; the hydrometer is the referee for the last percent.

Where this runs daily: proofing barrel spirits to bottling strength, cutting overproof rum for tiki specs, building liqueurs (where the “water” arrives as syrup — count it), tincture standardization in herbal practice, and vanilla extract (FDA minimum 35% ABV — dilute 95% spirit with 1.71× its volume of water… precisely: 750 × 95/35 = 2,036 mL final, 1,286 mL water, as a second worked example of the same division). Work clean: distilled or demineralized water for spirits that will sit (tap minerals cloud delicate liqueurs — the louche in limoncello is oils, but haze from hard water is forever).

Worked Examples (Verified)

  • Defaults: 750 mL at 95% → 40%: add 1,031 mL water, final ≈ 1,781 mL.
  • Vanilla extract strength: 750 mL at 95% → 35%: final 2,036 mL, add 1,286 mL.
  • Gentle cut: 1,000 mL of 63% barrel-proof whiskey → 45%: final 1,400 mL, add 400 mL — the distiller’s everyday proofing.

Dilution Discipline

  • Add water to spirit in stages and measure: contraction means the arithmetic overshoots volume slightly — you can always add more water; removing it is distillation (and, unlicensed, a legal problem in many places).
  • Measure ABV at the calibration temperature of your instrument (20 °C for most alcoholmeters); warm samples read low-density and overstate weakness.
  • Rest diluted spirits: freshly mixed spirit and water taste harsh and “separate” for days — a week of marrying transforms limoncello cuts; judge the recipe after the rest, not at the funnel.
  • Sugar changes volume and perceived strength: in liqueurs, dissolve sugar into the dilution liquid and treat syrup volume as your water figure; sweetness masks alcohol heat but the ABV math is untouched.
  • Mind local law: diluting purchased spirits for home liqueurs is broadly fine; distilling or redistilling (including “fixing” a dilution by boiling off water) is regulated nearly everywhere.

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Frequently Asked Questions

How do you calculate dilution of alcohol?

Final volume V₂ = V₁ × (starting ABV ÷ target ABV); water to add = V₂ − V₁. For 750 mL at 95% targeting 40%: V₂ = 750 × 95/40 = 1,781 mL, so add ≈ 1,031 mL water. This calculator does the division and flags the volume-contraction correction that precise work confirms by hydrometer.

Why doesn’t the final volume equal spirit plus water added?

Ethanol–water mixtures contract: the molecules pack more tightly together (hydrogen bonding), so 500 mL + 500 mL yields roughly 965–970 mL, not 1,000. The effect peaks near mid-range strengths (~3–4%) and vanishes at the extremes. Legal bottling uses gauging tables accounting for it; home liqueur work just proofs after mixing and trims — the arithmetic here is the right first addition.

How much water to make 40% vodka from 95% spirit?

Per litre of 95%: final volume = 1000 × 95/40 = 2,375 mL, so add ~1,375 mL water per litre (our 750 mL default: 1,031 mL). Chill- or charcoal-filter after dilution if you want commercial smoothness, rest it a week, and proof it at 20 °C for record-keeping.

Can I dilute with juice or syrup instead of water?

Yes — the math only tracks the ADDED VOLUME and the alcohol stays constant, so any non-alcoholic liquid counts as the diluent (syrup, juice, tea). Two caveats: sugary liquids change the final volume contribution slightly via their own densities, and flavors/sugars alter perceived strength without changing ABV. Measure the finished volume if the ABV claim matters.

What ABV do liqueurs usually target?

Commercial liqueurs cluster at 20–30% (limoncello ~26–32%, coffee liqueurs ~20–27%, amari 16–35%), creams lower, and herbal bitters-for-dashing higher. Home recipes mimic the target pour: dilute your macerated 95% base to the style’s band with syrup-as-diluent, then rest. Vanilla extract is regulated minimum 35% in the US — the worked example’s target.

Does dilution affect flavor extraction in tinctures?

Profoundly — but the ORDER matters: extract at high strength first (many target compounds are alcohol-soluble; 95% pulls resins and aromatics water can’t touch), then dilute the finished tincture to serving/preservation strength with this arithmetic. Diluting before extraction lowers the solvent power permanently for that batch; you cannot un-dilute an extraction.

How do I measure the result accurately?

An alcoholmeter (proof hydrometer) floated in a cylinder of the blend at its calibration temperature (usually 20 °C/68 °F), spun to shed bubbles, read at the meniscus. Sugar present invalidates hydrometer readings (density is no longer alcohol-only) — proof liqueurs BEFORE sweetening, or use the calculator’s conservation math as the record. Distillers use ebulliometers/distillation assays for sweet products.

Is this alcohol dilution calculator free?

Yes — free, instant, no sign-up. Enter starting volume and ABV plus target ABV for water to add and final volume, with contraction guidance.