Alcohol Dilution Calculator - Cross-Method Dilution Math

An alcohol dilution calculator uses the Pearson square to combine a strong spirit with water or a weaker spirit so the finished drink lands on a target ABV. The tool returns the exact diluent volume, the contraction loss, the pure alcohol grams, and the US and UK proof, and it works for 95% rectified spirit, 91% isopropyl alcohol, and any other high proof stock.

• • Bring 95% spirit down to 40% vodka: Dilute rectified spirit with water to reach standard vodka strength, then bottle the result with the exact ABV on the label.
• • Convert 91% isopropyl alcohol to 70%: Add the right amount of water so rubbing alcohol hits the 70% concentration recommended for surface disinfection.
• • Build homemade liqueurs: Pick a target ABV between 25% and 40% and combine a strong base spirit with sugar syrup, juice, or honey while keeping the proof consistent.
• • Bottle cask whisky at drinking proof: Reduce a 60% cask sample to a 46% bottling proof by adding the calculated water volume, which keeps the flavor profile intact while taming the burn.

The same logic covers blending two spirits, such as a 40% vodka with a 20% vermouth to hit a 30% aperitif strength, because the diluent does not have to be water. The only rule is that the target ABV has to sit between the diluent ABV and the strong ABV. If the target falls outside that range, the calculator flags the request.

The result panel reports the diluent volume before contraction and the smaller final volume after contraction, so you can plan a measured glass or a bottling tank with confidence.

When the batch is already mixed and you need the final percent, proof, and standard drink count from a single ABV label, Alcohol By Volume Calculator runs the reverse math in one screen.

The calculator uses the Pearson square to translate your inputs into a diluent volume, then layers a published contraction table and the NIST ethanol density to recover the final volume, mass, and proof.

• V_strong: Volume of the strong spirit you are diluting, in milliliters
• A_strong: ABV of the strong spirit, in percent
• A_diluent: ABV of the diluent, in percent (0 for water)
• A_target: Final ABV you want after mixing, in percent

The Pearson square keeps the calculation linear, so the diluent volume falls out as a single ratio once you know the strong and diluent ABVs and the target. The target must sit strictly between the two ABVs because a target above the strong spirit or below the diluent is impossible without distillation.

Once the diluent volume is known, the calculator multiplies the strong spirit volume by its ABV fraction to recover the pure alcohol volume, then multiplies by 0.789 g/mL for the mass. The result panel also reports US proof (ABV times 2, per 27 CFR 30.11), UK proof (times 1.75), and the standard drink count for the batch.

According to NIAAA, one US standard drink contains about 14 g of pure alcohol, the amount in 12 fl oz of 5% beer, 5 fl oz of 12% wine, or 1.5 fl oz of 40% spirits.

According to NIST Chemistry WebBook, pure ethanol has a density of 0.789 g/mL at 20 C, which converts pure alcohol volume to mass without losing precision.

Once the diluted batch is ready, scale the per-guest serving count with Party Drink Calculator so the punch bowl and the bottle count line up before the guests arrive.

Four short definitions keep the dilution math honest when you mix spirits, scale homemade liqueurs, or read labels across proof systems.

These four ideas show up in nearly every homemade liqueur and batched cocktail. Keeping the ratio method, the contraction effect, the two proof scales, and the mass-based standard drink straight prevents off-by-a-factor-of-two mistakes when you scale a recipe or read a foreign bottle.

If your recipe lists fluid ounces, tablespoons, or cups instead of milliliters, Cooking Measurement Converter handles those unit swaps before you enter the strong spirit volume here.

Run through these steps whenever you mix, dilute, or bottle a spirit at home.

1. 1 Enter the strong spirit ABV: Type the percent from the bottle label: 95 for rectified spirit, 40 for vodka, 91 for isopropyl alcohol, 60 for cask whisky.
2. 2 Enter the diluent ABV: Type 0 for water, juice, or sugar syrup. Type the labeled percent when blending two spirits, for example 20 for vermouth in a 30% aperitif.
3. 3 Choose the target ABV: Type the final percent you want. It must sit between the diluent and strong ABVs, otherwise the calculator flags the request.
4. 4 Enter the strong spirit volume: Type the milliliters of strong spirit you have. The calculator scales every other output from this number.
5. 5 Read the diluent and contraction: The result panel reports the exact diluent volume to add, the total before contraction, and the smaller final volume after ethanol and water pack together.
6. 6 Mix, bottle, and confirm the proof: Add the diluent, stir gently, and confirm the target ABV with a hydrometer before bottling.

To turn 500 mL of 95% rectified spirit into 40% vodka, enter 95, 0, 40, and 500. The result panel shows 687.5 mL of diluent, 1187.5 mL total volume, and 374.8 g of pure alcohol - about 26.8 US standard drinks.

When the dilution drives a per-bottle cost for a homemade liqueur or a small commercial batch, Recipe Cost Calculator picks up the ingredient pricing on the other side of the proof math.

Each output solves a real decision home bartenders, distillers, and brewers make every week.

• • Reliable Pearson square math: Replace the manual cross diagram with a single diluent volume you can trust, and avoid the off-by-one errors that happen when the strong and diluent numbers are read off a paper grid.
• • Honest mixture volumes: See the volume you add and the smaller volume you actually pour after contraction, so your measured glass and your bottling tank both come out right.
• • Standard drink and proof at a glance: Read the standard drink count and the US or UK proof next to the recipe, which keeps the batch aligned with low-risk drinking guidelines and with the label rules in each market.
• • Works for spirits and for cleaning solutions: Use the same form for 95% rectified spirit, 91% isopropyl alcohol, or any other high proof stock.
• • Bottle-to-bottle consistency: Match a target ABV exactly from one batch to the next, which is the key to a repeatable homemade liqueur or balanced bottled cocktail.

Because every result is derived from the same Pearson square ratio, contraction table, and ethanol density, the diluent volume, final volume, mass, and proof stay internally consistent. You never have to wonder whether two columns on the same page disagree.

A few real-world variables move the diluent volume and the final proof beyond the simple ratio math.

• • The Pearson square assumes ideal mixing between the two liquids. Three-ingredient dilutions still work, but the diluent must be entered as a single weighted ABV and the math does not track which ingredient is which.
• • The contraction table is a 1 L reference scaled linearly to the total mixture volume. Very small batches under 50 mL can show a different loss in practice because pouring and surface losses dominate, so read the diluent volume as a starting point and confirm with a hydrometer.

The contraction table comes from a published 1 L reference and is scaled by total mixture volume, the same approach used by home distillers and brewing software. Confirm with a hydrometer if the proof matters for compliance.

According to eCFR 27 CFR 30.11, US proof is the ethyl alcohol content of a liquid at 60 degrees Fahrenheit, stated as exactly twice the percent of ethyl alcohol by volume.

For sugar syrups and honey diluents that change the mixture density, Ingredient Volume to Weight Converter converts the sugar mass into the milliliters you need to enter as the diluent volume.