What is the legal blood alcohol limit in Australia?
The general limit is 0.05, but the zero-limit categories cover far more drivers than learners and P-platers — and no calculation can tell you which side of a limit you are on.
The short answer
0.05 for a full licence holder. A zero limit applies to learner, provisional and probationary drivers, and to drivers of heavy vehicles, public passenger vehicles and dangerous goods vehicles. Limits are set by each state and territory, so the zero-limit categories vary in detail.
The zero-limit group is bigger than people think
Most drivers know that learners and P-platers have a zero limit. Fewer know how far it extends.
Depending on the state, a zero limit also applies to drivers of heavy vehicles above a specified mass, public passenger vehicles including taxis and rideshare, driving instructors while instructing, and vehicles carrying dangerous goods.
An unrestricted driver in one state may fall into a zero-limit category in another, or when driving a different class of vehicle. Zero means zero — there is no allowance for a single drink, and a reading that would be irrelevant on a full licence is an offence.
A standard drink is a measure of alcohol, not volume
One Australian standard drink contains 10 grams of alcohol. Almost nothing you are served is exactly one.
A middy of full-strength beer is about 1.1 standard drinks; a schooner about 1.6; a pint around 2.1. A restaurant pour of wine is roughly 1.5, and a generous pour at home can be 2.5 or more. A 30 mL nip of spirits is exactly one, which is why spirits are the easiest thing to count and the hardest to pour consistently.
The home pour is where every estimate falls apart. Four glasses of wine poured at home can easily be ten standard drinks rather than the six somebody counted.
Why an estimate cannot answer the question
The Widmark equation is the standard method for estimating blood alcohol from consumption, and it is a population model. Its constants — the distribution ratio and the elimination rate — are averages with real variation between individuals.
Elimination runs at roughly 0.015 per hour, but published ranges span 0.010 to 0.020. Two people of identical mass who drank identically can measure differently depending on food, hydration, medication, fatigue and liver function.
That spread is wider than the gap any estimate is trying to measure. A calculated 0.048 against a 0.05 limit is not a pass — it is a number that cannot distinguish over from under.
The only measurement with legal standing is one taken by police. Nothing calculated has any status at all.
The morning after is the common offence
Elimination is slow and nothing speeds it up. A peak of 0.15 takes about ten hours to clear, so someone who stopped drinking at 2 am can still be over 0.05 at 7 am and over zero well past mid-morning.
Coffee, a cold shower, food, exercise and sleep all change how alert someone feels. None of them changes the rate at which the liver metabolises alcohol. Feeling fine is not evidence of a low reading, and that gap between feeling and measurement is exactly why morning-after offences are so common among people who genuinely believed they had waited long enough.
Where these numbers come from
- Australian Government Department of Health — standard drinks One standard drink contains 10 g of alcohol
- National Health and Medical Research Council — alcohol guidelines Australian guidelines on alcohol consumption
- Widmark equation — standard forensic and clinical method Distribution ratio and elimination rate
Method last reviewed 2026-10-28 This guide is re-checked against the sources above at least once a year, and again whenever a rule it explains changes. Out of date? Tell us and we will fix it.