Alcohol dilution in the UK context
In the UK, alcohol units are measured differently from most of Europe: 1 UK unit = 8g of pure alcohol (not 10g as in France or Spain). A standard 25ml measure of 40% ABV spirit contains exactly 1 unit. This calculator works in ABV (% vol.) and volumes (ml or litres), making it directly applicable to UK home distilling, cask dilution, and cocktail preparation.
CAMRA (Campaign for Real Ale) and UK cask ale producers routinely dilute cask ales from cellar strength to serving strength. The UK Food Standards Agency sets labelling requirements for alcoholic drinks sold at 1.2% ABV and above.
UK low-strength drinks context
Since the mid-2010s, low-ABV (2.5-3.5%) and alcohol-free products have grown rapidly in UK retail. Several craft breweries now produce cask ales at 2.8% ABV specifically to qualify for lower duty rates under UK Alcohol Duty rules. Dilution calculations matter for these products just as much as for full-strength spirits.
Common UK dilution targets
| Product | Typical ABV | UK units per 25ml |
|---|---|---|
| Standard spirits (whisky, vodka, gin) | 40 % | 1.0 |
| Cask strength whisky (Scotch) | 55-65 % | 1.4-1.6 |
| Navy strength gin | 57 % | 1.4 |
| UK cask ale (low duty) | 2.8 % | 0.07 per 25ml |
| Fortified wine (port, sherry) | 17-21 % | 0.4-0.5 |
Volume contraction note
Water and ethanol mix with a slight contraction , the combined volume is slightly less than the sum of the parts (~3% at 50% ABV). For distillery-precision bottling, apply a contraction correction using published HMRC or AOAC alcohol tables. For home use and cocktails, the simple formula is sufficient.
Indicative only. Drink Responsibly. This calculator does not constitute professional guidance on alcohol production or taxation. Consult a qualified professional for commercial applications.