A UK unit and a US standard drink measure different amounts of pure alcohol. Keep the convention beside every total. The number of glasses, cans or bottles alone is not a standardized alcohol amount.
Name the measurement system first
The NHS defines one UK unit as 10 mL or 8 g of pure alcohol. NIAAA defines one US standard drink as about 14 g of pure alcohol. A total of “four drinks” is therefore ambiguous unless you know whether it means four containers, four UK units or four US standard drinks.
These definitions describe quantities. They do not establish that an amount is safe for a particular person, predict intoxication or tell you when you can drive. Never turn a unit count into a countdown to driving or other safety-critical activity.
Keep three layers of information
Preserve the original container or pour description, the amount consumed and the stated strength. Then add the calculated quantity with its named convention. This allows someone to understand the record even if they use a different system.
ABV is alcohol by volume, expressed as a percentage. The NHS formula for UK units is consumed volume in mL multiplied by the numerical ABV percentage, divided by 1,000. Enter 4 for 4% in that formula, not 0.04.
| Record field | Illustrative entry |
|---|---|
| Drink description | One can, label retained |
| Consumed amount | 500 mL |
| Strength | 4% ABV |
| Calculation convention | UK units |
| Calculated amount | 500 × 4 ÷ 1,000 = 2 UK units |
| Unknowns | None for this invented quantity example |
Why you cannot copy the number across
In the example, two UK units correspond to 16 g using the UK gram definition. Dividing 16 by the US 14 g definition gives approximately 1.14 US standard drinks. The underlying drink has not changed; the measuring convention has. This is an approximate definition-based comparison, not a laboratory analysis.
If an app lets you switch conventions, check whether it converts existing amounts or merely changes a label. Keep the original volume and ABV so a mistaken display setting does not erase the source information. If the behavior is undocumented, do not assume the history has been converted correctly.
Original conversion example: 500 mL at 4% ABV = 2 UK units. Using 8 g per UK unit, that is 16 g; 16 ÷ 14 ≈ 1.14 US standard drinks. This describes quantity, not intoxication or a safe intake.
Do not invent strength to make a complete total
A mixed drink with unknown measures cannot be made accurate just by choosing “one cocktail.” Keep the ingredients or menu description you know and mark the amount or strength as uncertain. A container shared with others also requires your own consumed amount, not the bottle’s entire volume.
For a weekly summary, use the same convention throughout and keep uncertain entries visible. A total that excludes unknown drinks should be labeled as a known subtotal, not the entire week. Avoid decimal precision that hides a rough pour estimate.
Bring the original record when asking for help
The drink size and strength guide covers individual entries. Our alcohol calculator uses UK units and cannot estimate blood alcohol or driving safety. The free log or optional app can preserve the source information.
If you think you may be dependent on alcohol, seek medical advice before stopping suddenly; withdrawal can be dangerous. Seek urgent help for severe withdrawal symptoms such as seizures, hallucinations or marked confusion. A tracking total cannot determine whether stopping without medical support is safe.
Sources & checks
- NHS: Alcohol units ↗
UK unit definition and volume/ABV formula.
- NIAAA: What is a standard drink? ↗
US 14-gram definition and variable alcohol strength.
- NHS: Alcohol support ↗
Dependence and withdrawal safety; checked September 30.
- Current App Store listing: Alcohol Tracker+ ↗
Public US listing checked September 30; recording or sound features only, not evidence of health benefit.
Checked against these sources on 2026-09-30. Examples and worksheets are original illustrations, not real patient histories or clinical validation. This is educational content, not individual medical advice or a clinician-reviewed treatment plan.
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