Why a “standard drink” changes when you switch countries
Governments publish drinking guidance in their own counting systems. Swapping regions on this page
does not just relabel the same number: it swaps the underlying definition of one drink of alcohol,
because each system anchors to a different mass of ethanol.
| Region |
Ethanol in one counted drink |
Typical formula used here |
| United Kingdom |
10 ml pure alcohol (~7.9 g ethanol by mass) |
millilitres × ABV% ÷ 1,000 = UK units |
| United States |
14 g pure alcohol (0.6 US fl oz) |
US fl oz × ABV% ÷ 60 = US standard drinks |
| Australia (NHMRC 2020) |
10 g pure alcohol |
millilitres × ABV% ÷ 1,250 = Australian standard drinks |
Practical takeaway: a 750 ml bottle of 12% wine is about 9 UK units,
roughly five US standard drinks, and about 7.2 Australian standard drinks.
If you are comparing notes with a friend overseas, compare grams of ethanol or the inputs (volume + ABV),
not only the headline count.
Official definitions and guidance are published by national health bodies; authoritative links are collected
in the final guide below.
How to use the calculator end-to-end
1. Pick the jurisdiction you want numbers for
Use the region control at the top of the page before you start logging drinks. That choice drives preset
pours (for example UK pints vs US fluid ounces), the text in the FAQ, the guideline bands in the weekly
tracker, and which legal BAC limits appear in the driving panel.
2. Log pours as they happen
Start from the curated list if it matches what you are drinking, or open Custom drink
and type the volume printed on the can or menu plus the ABV from the label. The quantity buttons are there
for rounds: add three identical bottles once instead of clicking three times.
3. Save sessions into the weekly chart
When a night is finished, press Save to weekly tracker so the bar chart can show how that
evening sat against the low-risk bands configured for your region. The chart is stored with your other data
in localStorage only on this device, which keeps the tool usable offline
and avoids sending consumption data over the network.
What the coloured guideline bars represent
The tracker is a visual reference, not a medical diagnosis. Each country expresses risk differently, so the
bars mirror the same limits encoded in the app:
- United Kingdom: Chief Medical Officers recommend staying at or below 14 units every
week, spread across at least three days, with several completely alcohol-free days.
- Australia: NHMRC 2020 recommends no more than 10 standard drinks in any week and no more
than 4 on a single day to reduce lifetime risk, with zero alcohol for people who are pregnant, planning
pregnancy, or under 18.
- United States: the Dietary Guidelines describe daily moderation (up to two standard
drinks for men and one for women) rather than a single weekly cap; this site also plots weekly totals of
24/12 drinks as a planning aid aligned with those daily ceilings—discuss personal targets with a doctor if
you have liver disease, take sedating medicines, or are in recovery.
Heavy episodic drinking carries risks even when a weekly average looks acceptable, which is why Australian
guidance calls out the per-day cap explicitly and UK messaging stresses spacing drinks out.
Where calorie estimates come from (and what they miss)
Ethanol yields about 7 kilocalories per gram. The calorie column on this site multiplies the
ethanol mass implied by your volume and ABV by that constant. It therefore captures the energy in the alcohol
itself, but not carbohydrates from beer malt, residual sugar in wine, or syrups in cocktails unless you
model them as a separate custom drink with a higher effective ABV or note them mentally.
That trade-off is intentional: labelled ABV is regulated and comparable between brands, while sugar content is
often missing from packaging. Treat the calorie figure as a floor for spirits-forward drinks and an
approximation for beer and wine—still useful for spotting how quickly a social evening adds hidden energy.
BAC estimates, elimination, and why “coffee sober” is a myth
The When can I drive? card applies the textbook Widmark relationship between ethanol dose,
distribution volume, and body weight, then subtracts a conservative average elimination slope of about
0.015% BAC per hour to show when modelled BAC crosses the legal thresholds listed for your
region. Gender defaults adjust the body-water fraction (r = 0.73 male, 0.66 female) inside the same
formula forensic labs use for back-of-envelope work.
Food before drinking, medications, sleep deprivation, and individual liver enzyme expression can shift both
peak BAC and clearance speed. Caffeine masks sedation; it does not remove ethanol. If you still feel tired,
dizzy, or slow, do not drive even if the timeline reads zero hours remaining.
Workplace testing, medical procedures, and zero-alcohol licence conditions can be stricter than the general
road limits shown here—always follow the specific rule set that applies to you.
ABV labels, glassware, and why home pours drift high
Packaged drinks must declare alcohol by volume, but bars and kitchens rarely pour exactly the reference serve
used in marketing copy. A “large wine” in one venue may be 250 ml while another stops at 175 ml; craft beer
pints may exceed mainstream ABV. When in doubt, measure once with a kitchen scale or measuring jug and save
that volume as a custom preset mentally—small errors in ABV compound across several rounds.
Headspace in a pint glass, foam, and shared pitchers also change how much liquid you actually swallow compared
with the volume you type. Logging conservatively (round up ABV, round down volume) gives a safer planning window
for driving estimates.
Authoritative sources for further reading: