Alcohol Dilution Calculator

How to use this alcohol dilution calculator

What this calculator does

This calculator estimates the amount of water or a weaker alcohol solution needed to reduce a stronger solution to a chosen alcohol-by-volume concentration. It applies a volume balance: the pure alcohol already present in the strong liquid must equal the pure alcohol in the combined mixture. It is useful for beverage formulation, tincture planning, cleaning-solution preparation, and laboratory-style pre-calculation. It does not verify legal proof, purity, temperature corrections, density, product safety, or whether a mixture is suitable for drinking, medical use, disinfection, or sale.

When to use it

Use it when you need to dilute high-proof spirit with water, blend a stronger and weaker beverage, estimate a batch before measuring, or compare how a target concentration changes the amount of diluent required. For regulated production or exact proofing, use calibrated instruments and the official procedures applicable to your work.

How to calculate

1. The calculator opens with a ready-to-use demonstration: 500 mL of 95% alcohol, 0% water, and a 40% target. The results and a validated example Excel workbook are available immediately.
2. Replace the three concentration values and the strong-liquid volume with your own figures. Choose mL, L, or US fl oz from the volume selector; changing the unit converts the current volume rather than merely relabeling it.
3. Leave Estimate alcohol contraction volume selected for a rough post-mixing volume estimate, or clear it to use the exact additive-volume result only.
4. Read the amount shown under Water / weak alcohol to add, then review the final volume, contraction estimate, pure alcohol volume, ratio pill, and mixture table.
5. Select Download Excel to export the current typed inputs and canonical results. Reset clears the demonstration data and results; Excel export remains unavailable until a complete valid scenario is entered again.

Input guide

Strong alcohol concentration is required and accepts a decimal percentage from above 0 to 100, such as 95. It must exceed the target. A higher value generally requires more weak liquid for the same target and strong-liquid volume. Do not enter proof as though it were ABV; for example, 80 US proof is 40% ABV.

Water / weak alcohol concentration is required and accepts 0 to below 100% ABV. Enter 0 for water or, for example, 20 for a weaker spirit. It must be lower than the target. Increasing it reduces the amount needed because the added liquid also contributes alcohol.

Target concentration is required and must be strictly between the weak and strong concentrations. A realistic beverage example is 40%. Moving the target closer to the strong concentration lowers the required added volume; moving it closer to the weak concentration increases it sharply.

Strong alcohol volume is a required positive decimal. The demonstration uses 500 mL. The result scales directly: doubling this volume doubles every calculated volume. The parser uses a dot as the decimal separator and rejects scientific notation or ambiguous decimal-comma input. Volume unit chooses mL, L, or US fl oz and converts the current amount using standard volume relationships; NIST explains that 1 liter equals 1,000 milliliters.

Estimate alcohol contraction volume is optional. When selected, the calculator interpolates an approximate volume loss from a concentration-based reference table and subtracts it from the additive total. Real contraction depends on composition and temperature, so treat this as a planning estimate rather than an exact correction.

Output guide

Water / weak alcohol to add is the primary calculated diluent volume in your selected unit. Final volume before contraction is the exact sum of the two entered or calculated component volumes under the additive-volume model. Estimated contraction is zero when the option is off and otherwise shows the approximate shrinkage. Estimated final volume subtracts that estimate. Pure alcohol volume is an identity derived from the strong volume times its ABV fraction. The pills summarize the strong-to-weak ratio, target ABV, and estimated final volume. The table lists each component's concentration, volume, and pure-alcohol contribution, plus the combined pre-contraction total.

Worked example

For the opening example, pure alcohol equals 500 mL × 0.95 = 475 mL. To obtain 40% ABV using water, the final additive volume must be 475 ÷ 0.40 = 1,187.50 mL. Therefore, water to add is 1,187.50 – 500 = 687.50 mL. At a 40% target, the optional table-based estimate is 29 mL lost per liter of additive mixture, so the estimated contraction is 1.1875 × 29 = 34.44 mL and the estimated final volume is 1,153.06 mL.

Learn more

For unit notation and conversions, consult the NIST guidance on writing SI units. For chemical properties and safety context, review the NIH PubChem ethanol record. Ethanol is flammable, and concentration calculations alone do not establish safe handling or suitability.