Spirit Dilution to Bottling Strength Calculator

How it works

This spirit dilution calculator uses the standard volume-based dilution formula — a practical version of the chemistry shortcut C1V1 = C2V2 — to work out how much water to add when cutting a high-proof spirit down to a standard bottling strength. Whether you’re using it as a distilling calculator for new-make spirit straight off the still, an alcohol distillation calculator for cutting cask-strength stock, or simply a bottling strength calculator for a batch you’ve already purchased, the underlying maths is the same scaled-water calculation:

Water to add (mL) = Current volume (mL) × (Current ABV ÷ Target ABV − 1)
Final volume (mL) = Current volume (mL) + Water to add (mL)
Bottles (700mL) = Final volume (mL) ÷ 700

The calculator ships with four common Australian bottling presets — vodka at 37% ABV (the local minimum), gin at 40% ABV, whisky at 43% ABV and rum at 37.5% ABV — or you can switch to a custom target and enter any ABV you like. Because adding water only spreads the existing alcohol across more liquid, the total pure alcohol in the batch never changes; only its concentration and volume do, a point worth keeping in mind alongside the Department of Health’s standard drinks guide, which defines a standard drink as 10 grams of pure alcohol.

One important note before you use this tool: in Australia, distilling spirits — even at home, even for personal use — is illegal without an excise manufacturer licence from the ATO, as set out on the ATO’s page on excise and excise-equivalent goods. That’s different from homebrewing beer, cider, wine or mead, which is legal for personal use without a licence. This calculator is built for two situations only: licensed distillers cutting a finished batch down to bottling strength, and anyone diluting an already-purchased, legally-obtained high-proof spirit.

Worked example

Priya runs a small licensed craft distillery in the Adelaide Hills, South Australia, holding an ATO excise manufacturer licence that lets her legally produce and sell spirits. A fresh run of new-make spirit comes off her still at 1,000mL and 65% ABV — far too hot to bottle as gin, and well above the strength her customers expect on the shelf. She wants to bring it down to a standard 40% ABV for her flagship bottling, so she reaches for a spirit dilution calculator rather than guessing with a jug of water.

Using the formula: 1,000 × (65 ÷ 40 − 1) = 625mL of water. Adding that to her 1,000mL of new-make gives her 1,625mL of spirit at 40% ABV — enough for a little over two standard 700mL bottles, with roughly 225mL left over to top up a smaller bottle or add to the next batch. She logs the volumes for her excise records, then filters and bottles the finished gin.

	ABV	Volume	700mL bottles
Before dilution	65%	1,000mL	1.43
After dilution	40%	1,625mL	2.32