The same drink gets measured differently depending where you live. A UK unit isn’t an American standard drink. An Australian standard drink isn’t a European gram. The fragmentation isn’t accidental; different countries developed their drinking guidelines independently and chose different anchor measurements. The result is that “two units” means something specific in the UK, “two standard drinks” means something else in the US, and the published health guidelines aren’t directly comparable across borders. This guide covers what each system actually measures, why they differ, and how to convert when you need to.
This is the pillar of our Alcohol Units hub. Sub-articles will go deeper on specific calculations and regional definitions as the hub fills out.
# What a unit actually measures
Underneath all the regional variation, every system is measuring the same physical thing: the volume of pure ethanol in a drink, expressed in either grams or millilitres.
Pure ethanol weighs roughly 0.79 grams per millilitre. So 10ml of pure alcohol weighs 7.9g, and 14g of pure alcohol takes up about 17.7ml. The conversion between volume and weight is consistent; it’s just a matter of which the local guidelines use.
The fundamental question every system answers: how much pure alcohol is in this drink? The answer depends on three things:
Volume of the drink (how much liquid is in the glass)
ABV (the percentage of that liquid that’s alcohol)
Density of alcohol (constant: 0.79g/ml)
Once you know the volume and ABV, the alcohol content is fixed regardless of which “unit” system you express it in. The systems differ only in how they label the same underlying number.
# The major systems
The four most common measurement systems:
# UK alcohol units
A UK unit equals 10ml or 8 grams of pure alcohol.
The formula: units = (volume in ml × ABV) ÷ 1000
So a 568ml pint of 4% lager is (568 × 4) ÷ 1000 = 2.27 units. A 175ml glass of 13% wine is (175 × 13) ÷ 1000 = 2.275 units.
The UK low-risk drinking guideline is 14 units per week, spread across at least 3 days, with several drink-free days. This applies equally to men and women.
The 10ml-per-unit choice was originally about giving a round number for the “average” pub measure of spirits (25ml at 40% = 1 unit). The system extends that to all drinks.
# US standard drinks
A US standard drink equals 14 grams of pure alcohol, which works out to approximately 17.7ml.
Common US standard drinks:
- 12oz (355ml) of 5% ABV beer: 14g of alcohol
- 5oz (148ml) of 12% ABV wine: 14g of alcohol
- 1.5oz (44ml) of 40% ABV spirit: 14g of alcohol
The US guidelines suggest no more than 2 standard drinks per day for men and 1 for women, with non-drinking days encouraged.
A US standard drink contains 1.75x the alcohol of a UK unit (14g vs 8g). When converting:
- 1 US standard drink = 1.75 UK units
- 1 UK unit = 0.57 US standard drinks
# Australian standard drinks
An Australian standard drink equals 10 grams of pure alcohol (12.5ml).
Common Australian standard drinks:
- 285ml of 4.8% beer (a “middy”): 1 standard drink
- 100ml of 13% wine: 1 standard drink
- 30ml of 40% spirit (a standard pub measure): 1 standard drink
The Australian guidelines suggest no more than 10 standard drinks per week and no more than 4 standard drinks on any single day.
Australian standard drinks contain 25% more alcohol than a UK unit (10g vs 8g). When converting:
- 1 Australian standard drink = 1.25 UK units
- 1 UK unit = 0.8 Australian standard drinks
# European grams of pure alcohol
Many European countries use grams of pure alcohol directly rather than “units.” Denmark, Sweden, Norway, the Netherlands, and others reference drinking guidelines in grams.
The grams system is straightforward: you measure or calculate the actual grams of ethanol per drink and add up. Most European guidelines suggest 100-140g of alcohol per week as a low-risk threshold.
A 175ml glass of 13% wine contains:
- Volume of alcohol: 175 × 0.13 = 22.75ml
- Mass of alcohol: 22.75 × 0.79 = 18g
So that glass of wine is 18g of pure alcohol, which corresponds to 2.25 UK units, 1.3 US standard drinks, or 1.8 Australian standard drinks.
# Why the systems differ
The variation isn’t because alcohol is different in different countries. It’s because the “round number” each system chose was based on local drinking conventions:
UK chose 10ml because that gave a clean number for the standard 25ml pub measure of spirits at 40% ABV.
US chose 14g because that gave a clean number for a 12oz beer at 5% (the standard American beer size and strength) and a 1.5oz shot at 40%.
Australia chose 10g to align with European usage and to give a clean number for the older 7oz “middy” beer.
Europe chose grams because it’s the cleanest scientific unit and makes mathematical comparison easy.
The systems are equally valid. They’re just different conventions for measuring the same thing.
# The conversion shortcuts
If you need quick conversions:
| From | To | Multiplier |
|---|---|---|
| UK units | US standard drinks | × 0.57 |
| UK units | Australian standard drinks | × 0.8 |
| UK units | Grams of alcohol | × 8 |
| US standard drinks | UK units | × 1.75 |
| US standard drinks | Australian standard drinks | × 1.4 |
| US standard drinks | Grams of alcohol | × 14 |
| Australian standard drinks | UK units | × 1.25 |
| Australian standard drinks | US standard drinks | × 0.71 |
| Australian standard drinks | Grams of alcohol | × 10 |
For practical purposes, most people only need to convert between the system their country uses and one or two others. UK travellers in the US benefit from knowing 1 US drink ≈ 1.75 UK units. Americans in the UK benefit from knowing 14 UK units ≈ 8 US drinks.
# Why guidelines differ between countries
A common confusion: comparing drinking guidelines across countries makes it look like advice differs dramatically. The UK suggests 14 units a week. The US suggests up to 14 drinks per week for men. These sound similar but represent very different actual alcohol amounts.
Converting to a common measure:
- UK 14 units = 112 grams of alcohol per week
- US 14 standard drinks = 196 grams of alcohol per week
- Australia 10 standard drinks = 100 grams of alcohol per week
The US guidelines actually suggest 75% more alcohol per week than the UK guidelines for men. The difference reflects different national assessments of risk, different drinking cultures, and different policy goals.
The UK guidelines were updated downward in 2016 based on new cancer risk data; the US guidelines are reviewed periodically and have stayed relatively stable. Neither is “right” or “wrong”; they’re different judgements based on the same evidence.
For someone tracking their drinking, the practical implication is to use the system your local guidelines reference, then check what level your guidelines consider low-risk. Don’t assume “moderate” means the same thing across borders.
# Why pub and home measures differ from theory
The systems above describe theoretical “standard” drinks. Actual drinks at home, in pubs, and in restaurants frequently differ:
# Home pours of wine
The standard UK glass is 175ml. Home pours typically run 200-250ml. A “glass” of wine at home often contains 1.5x the units of a standard pub measure.
For tracking, the answer is to measure your home pour once and then either keep pouring that amount (and counting the appropriate units) or pour the standard measure and count one unit per glass.
# Home pours of spirits
The UK pub measure is 25ml (or 35ml in some venues). Home pours of spirits are typically 50-80ml, which is 2-3x larger than the pub measure.
This is where most home-drinking underestimation happens. Counting “a whisky at home” as one pub measure underestimates by 2-3x. We cover the underestimation patterns in Why You Always Underestimate How Much You Drink.
# Pints of varying strength
A “pint” doesn’t mean a fixed unit count. A pint of 3.5% bitter is 1.99 units. A pint of 6% IPA is 3.4 units. A pint of 8% imperial stout is 4.5 units. The same word, very different alcohol content.
People who count pints without recording strength systematically underestimate their alcohol intake.
# Cocktails
Cocktails vary substantially. A simple gin and tonic might have 1 unit (single pub measure of gin). A long island iced tea has 4-5 units (four different spirits in one glass). A cocktail isn’t “one drink” in the unit sense.
For tracking, recording the specific cocktail is more useful than counting “cocktails.”
# Restaurant pours
Restaurant wine pours often run 200-250ml rather than 175ml. Some restaurants serve “small” (125ml), “medium” (175ml), and “large” (250ml) glasses, and “medium” frequently means a generous 200ml pour.
The 250ml restaurant pour is roughly 1.5 units of standard wine, so a “couple of glasses” with dinner can easily be 5+ units total.
# Why all this matters for tracking
Once you know the unit system you’re using, tracking becomes a question of recording each drink accurately. The math is simple:
- Volume × ABV ÷ 1000 = UK units
- Or: volume × ABV × 0.79 ÷ 100 = grams of pure alcohol
Most modern tracking apps do this calculation automatically once you record what you drank. The hard part isn’t the math; it’s accurately recording the volume and ABV.
For people who track:
- Record what you actually drank, not what you usually drink
- Note the ABV when it’s outside the standard range (anything above 5% for beer or 13% for wine matters)
- Estimate home pours generously (most are larger than they feel)
- Convert to your local system so you can compare against guidelines
For people who don’t track formally, knowing the unit math at least helps with rough estimation. A pint of 5% lager is roughly 2.8 units. A 175ml glass of 13% wine is roughly 2.3 units. A 25ml shot of 40% spirit is roughly 1 unit. From those anchors you can estimate any session.
# Practical implications
Some patterns the unit system makes visible:
# Wine sessions add up faster than people think
Three “glasses” of red at home (typically 250ml each at 14% ABV) is 10.5 units. That’s three quarters of the UK weekly guideline in a single evening.
# Pints stack faster with strong beer
Five pints of 6% IPA is 17 units. That’s already over the UK weekly guideline in one session.
# Spirits at home add up fastest
Three “doubles” at home (typically 50-60ml each at 40% ABV) is 6-7 units, but more importantly, that’s the equivalent of 6-8 UK pub measures.
# “Moderate” guidelines are tighter than they sound
14 UK units a week sounds generous. In practice it’s roughly:
- 6 pints of 4% lager OR
- 4 pints of 5.5% IPA OR
- 6 medium glasses of 13% wine OR
- 14 single pub measures of spirits
Spread across a week, that’s 1-2 drinks most evenings, or a moderate weekend session. Most people who consider themselves “moderate drinkers” exceed the 14-unit guideline.
# How AlcoLog handles units
AlcoLog calculates units automatically based on your locale settings. UK users see UK units, US users see US standard drinks, Australian users see Australian standard drinks. The catalogue includes 273 drinks at 87 size presets, all with accurate ABV and volume data.
The session-end summary shows total drinks, total units (in your local system), and total calories. The History view aggregates these by week and month for the longer-term pattern view.
For drinks not in the catalogue (custom cocktails, unusual brands, particular home pours), the Add Drink screen lets you specify volume and ABV manually. The unit calculation happens automatically once you enter those values.
If you travel internationally and want to convert your AlcoLog data to a different system, the CSV export includes raw alcohol content data that can be converted to any system you need.
