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Estimate your Blood Alcohol Content (BAC) based on standard drinks, body weight, gender, and time elapsed. Uses Australian standard drinks (10g of pure alcohol).
Gender
Affects body water constant used in the Widmark formula
Estimated BAC
Enter your weight and number of drinks above to estimate your BAC.
Australian Legal BAC Limits
| Licence Type | BAC Limit | Notes |
|---|---|---|
| Full licence | 0.05 | All states and territories |
| Learner / Provisional | 0.00 | Zero BAC in all states and territories |
| Heavy vehicle (GVM > 15t) | 0.00 | Some states allow 0.02 for certain classes |
| Taxi / rideshare / bus | 0.00 | Zero BAC while operating commercially |
| Driving instructor | 0.00 | While supervising a learner |
WA, QLD, NSW, VIC, SA, TAS, NT, and ACT all use 0.05 for full licence holders.
Australian Standard Drinks
| Drink | Volume | Alcohol % | Std Drinks |
|---|---|---|---|
| Light beer | 375mL can | 2.7% | 0.8 |
| Mid-strength beer | 375mL can | 3.5% | 1 |
| Full-strength beer | 375mL can | 4.8% | 1.4 |
| Glass of wine | 150mL | 13% | 1.5 |
| Bottle of wine | 750mL | 13% | 7.7 |
| Spirit (nip) | 30mL | 40% | 1 |
| Spirit + mixer | 375mL premix can | 5% | 1.4 |
| Cocktail | varies | varies | 2 |
Click any row to add that number of standard drinks to your input. 1 Australian standard drink = 10g of pure alcohol.
What is BAC?
Blood Alcohol Content (BAC) is a measure of the amount of alcohol in your bloodstream, expressed in grams per 100 millilitres of blood (g/100mL) in Australia. A BAC of 0.05 means 0.05 grams of alcohol per 100mL of blood — the legal limit for full licence holders across all Australian states and territories.
Standard drinks in Australia
One Australian standard drink contains 10 grams of pure alcohol. This is different from the US standard (14g) and the UK unit (8g). Always check the label — the number of standard drinks is printed on all Australian alcohol packaging.
Factors that affect BAC
Many factors influence how quickly alcohol is absorbed and eliminated: whether you have eaten, your hydration level, liver health, medications, and body composition (muscle vs fat). Importantly, tolerance does not lower your BAC — it only reduces your perception of impairment. You can feel fine and still be over the limit.
Penalties
Drink driving is a criminal offence in Australia. Penalties vary by state but include on-the-spot fines, licence disqualification, alcohol interlock programs, and imprisonment for repeat or high-range offences. A drink driving conviction creates a criminal record that can affect employment, travel, and insurance.
The Widmark Formula
BAC (g/dL):
A / (r × W) − β × t
Where:
A = drinks × 10 (grams)
r = 0.68 (M) or 0.55 (F)
W = weight in grams
β = 0.015 g/dL per hour
t = hours elapsed
Your privacy
All calculations are performed entirely in your browser. No data about your weight, drinks, or BAC estimate is stored, transmitted, or logged. This page does not use cookies for tracking.
Australian resources
For information on alcohol and your health, visit the Australian Government guidelines or speak with your GP.
health.gov.au — AlcoholThis calculator uses the Widmark formula, the most widely accepted method for estimating Blood Alcohol Content. It accounts for the mass of alcohol consumed (in grams, based on Australian standard drinks of 10g each), your body weight, a gender-specific body water constant (0.68 for males, 0.55 for females), and the average metabolism rate of 0.015 g/dL per hour. The result is an estimate in g/100mL — the same unit used in Australian drink driving law. Individual results can vary significantly based on factors the formula does not capture, including food intake, hydration, liver function, and medications.
All Australian states and territories set the legal BAC limit at 0.05 g/100mL for full licence holders. Learner and provisional licence holders must maintain a zero BAC (0.00) at all times while driving. The same zero limit applies to drivers of heavy vehicles, taxis, buses, rideshare vehicles, and driving instructors supervising learners. Random breath testing (RBT) is conducted regularly by police across Australia. If you are unsure whether you are under the limit, the safest choice is always not to drive.