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Calculate beer IBU from hop additions, alpha acid percentage, boil time, and batch volume. Estimate bitterness for homebrew recipe design.
Calculate mash and sparge water volumes from grain bill weight, mash thickness, and target pre-boil volume for all-grain homebrewing.
Calculate priming sugar amount for bottle conditioning from batch volume and target volumes of CO2. Carbonate beer with corn sugar, DME, or honey.
Without contraction correction: water to add = (Starting volume × (Start ABV − Target ABV)) / Target ABV.
Water = V × (C1 − C2) / C2Mixing ethanol and water reduces total volume below the sum of parts — contraction is 2–4% at typical bottling dilutions. Adjusted formulas add 2–3% to calculated water volume.
Actual water ≈ Theoretical water × 1.03US proof is twice ABV. 100 proof = 50% ABV. 80 proof = 40% ABV. Use ABV consistently in dilution calculations.
ABV = Proof / 2Updated: July 2026
1 liter at 60% ABV to 46%: water = 1000 × (0.60 − 0.46) / 0.46 ≈ 304 mL. Add ~310 mL accounting for contraction. Final volume ~1.28 L.
750 mL at 65% ABV to 45% ABV: ~333 mL water needed. Add gradually, stir, and recheck with hydrometer or refractometer.
5 L at 95% ABV to 40%: water = 5000 × (0.95 − 0.40) / 0.40 = 6875 mL. Large dilution — add water slowly with agitation for even blending.
When diluting cask-strength (>55% ABV) to bottling strength, add 2–3% extra water beyond the simple formula, or measure ABV after partial dilution and adjust.
Convert proof to ABV first (divide by 2 in the US). Using 100 proof as 100% in the formula produces wildly incorrect water volumes.
Diluting high-proof spirits to bottling strength requires precise volume calculations to hit target ABV without over-diluting. This calculator uses the standard alcohol dilution formula accounting for volume contraction when mixing ethanol and water.