Understanding how much alcohol you are actually consuming requires more than reading the label — it requires converting volume and ABV into a meaningful unit. The Standard Drink Calculator does exactly that: it takes the volume of any drink in millilitres and its alcohol by volume (ABV) percentage, calculates the grams of pure ethanol, and translates that into the official standard-drink count for the United States, United Kingdom, Australia, or Canada. Because each country uses a different definition, the same glass of wine can simultaneously be 1.4 US standard drinks, 1.8 UK units, 1.9 Australian standard drinks, and 1.5 Canadian standard drinks. This tool shows all four.
How the formula works
The calculation starts with the physical chemistry of ethanol. Pure ethanol has a density of 0.789 g/mL at room temperature (20 °C). To find the grams of pure ethanol in any drink:
ethanol (g) = volume (mL) × (ABV / 100) × 0.789
A 355 mL (12 oz) regular beer at 5% ABV therefore contains 355 × 0.05 × 0.789 = 14.0 g of pure ethanol. Dividing by each country’s standard-drink benchmark gives the count in that system:
| Country | Grams per standard drink | 355 mL / 5% beer |
|---|---|---|
| United States | 14 g | 1.00 drink |
| Canada | 13.45 g | 1.04 drinks |
| Australia | 10 g | 1.40 drinks |
| United Kingdom | ~7.9 g (10 mL) | 1.78 units |
The UK system is defined in millilitres of pure ethanol rather than grams: one UK unit = 10 mL. Converting via density (10 mL × 0.789 g/mL = 7.9 g) makes it comparable with the others. The calculator applies this conversion internally so all four figures appear consistently.
Worked example
You share a 750 mL bottle of wine at 13% ABV between two people, pouring two equal glasses (375 mL each).
- Ethanol per glass = 375 × 0.13 × 0.789 = 38.5 g
- US standard drinks = 38.5 / 14 = 2.75
- UK units = 375 × 13 / 1000 = 4.9 units
- Australian standard drinks = 38.5 / 10 = 3.85
- Canadian standard drinks = 38.5 / 13.45 = 2.86
A single large wine glass like this already accounts for roughly one-fifth of the UK weekly guideline of 14 units — something that is invisible until you run the numbers.
Weekly guideline gauge
Below the result the calculator shows a colour-coded progress bar expressing your session total as a fraction of the standard weekly low-risk guideline for the selected country. Green indicates you are well within the guideline, amber that you are approaching it, and red that this session alone exceeds it. The gauge is informational only and does not account for cumulative weekly consumption; it simply contextualises a single session against official public-health figures.
Why the definitions differ
Standard drink definitions were set independently by each country’s health authorities, mostly in the 1980s and 1990s, before global harmonisation was a priority. The US National Institute on Alcohol Abuse and Alcoholism (NIAAA) anchored its 14 g figure to a typical American 12 oz beer. Drinkwise Australia chose 10 g to align with a small glass of wine. The UK system — introduced in 1987 — uses a volume-based unit (10 mL) rather than a weight-based one, reflecting different scientific conventions at the time. None of these choices is more “correct” than another; they are simply reference points for communicating risk.
This calculator is for informational purposes only and does not constitute medical advice. If you are concerned about your alcohol consumption, please speak with a healthcare professional.