Estimate your blood alcohol concentration (BAC) and time until sober. Australian legal drink-driving limits apply.
Blood alcohol content (BAC) is the percentage of alcohol in your bloodstream. A BAC of 0.05% means 0.05 grams of alcohol per 100 mL of blood. It rises as you drink and falls slowly as your liver processes alcohol — at a fixed rate that nothing can speed up. BAC calculators estimate this from your weight, sex, drinks and time.
⚠️ Important: This is an estimate only. BAC varies significantly with food, health, and individual factors. Do not drink and drive. In Australia: general licence BAC limit = 0.05; learner/P-plate = 0.00.
| Information | Value |
|---|
Most BAC calculators use the Widmark formula, which estimates blood alcohol from the amount of alcohol consumed, your body weight, a body-water constant, and time.
Alcohol affects judgement and coordination well before obvious drunkenness. This is a general guide, not a personal prediction.
| BAC | Typical Effects | Driving Impairment |
|---|---|---|
| 0.02% | Slight relaxation; some mood change | Some decline in visual function and multitasking |
| 0.05% | Lowered alertness; reduced inhibition | Reduced coordination and response — legal limit in many places |
| 0.08% | Impaired judgement and control | Significantly impaired; illegal to drive in many countries |
| 0.10% | Slurred speech; poor coordination | Seriously impaired |
| 0.15% | Major loss of balance and control | Extremely dangerous |
| 0.30%+ | Confusion, risk of unconsciousness | Life-threatening; risk of alcohol poisoning |
Drink-driving limits differ by country and can change. Always check the current local law — and remember lower is always safer.
| Country | General Driving Limit (BAC) |
|---|---|
| Australia | 0.05% (0.00% for learner/provisional) |
| United States | 0.08% (lower for under-21) |
| Canada | 0.08% federal (0.05% many provinces) |
| United Kingdom | 0.08% (0.05% in Scotland) |
| New Zealand | 0.05% |
| Germany | 0.05% (0.00% for novices) |
Limits shown are general adult figures and may have changed. Novice, professional and young drivers often face stricter limits.
Your body clears alcohol at a steady rate of roughly one standard drink per hour — and nothing speeds this up. Coffee, cold showers, exercise, water and fresh air may make you feel more alert, but they do not lower your BAC. Only time reduces alcohol in your blood.
BAC (Blood Alcohol Concentration) measures the percentage of alcohol in your bloodstream — specifically grams of alcohol per 100 millilitres of blood (g/100 mL). A BAC of 0.05 means 0.05g of alcohol per 100mL of blood. BAC is the legal standard used for drink driving enforcement in Australia and internationally.
| Driver Category | Legal BAC Limit | Consequence at Limit |
|---|---|---|
| Full licence holders | 0.05 BAC | Criminal charge; licence suspension |
| Learner drivers (L plates) | 0.00 BAC | Zero tolerance — any reading is an offence |
| P1 and P2 provisional drivers | 0.00 BAC | Zero tolerance |
| Professional/heavy vehicle drivers | 0.00 BAC | Zero tolerance |
| Cycling (varies by state) | 0.05 in most states | Varies by state law |
What is the legal BAC limit for driving in Australia?
The legal BAC limit for full licence holders in all Australian states and territories is 0.05 (0.05g of alcohol per 100mL of blood). Learner drivers, P1, P2 provisional drivers, professional drivers, and heavy vehicle operators must maintain 0.00 BAC. Exceeding these limits is a criminal offence carrying fines, licence suspension, and potentially imprisonment for high readings.
How long does alcohol stay in your system?
Alcohol is eliminated at approximately 0.015-0.02 BAC per hour regardless of how much you drink. Nothing accelerates this — not coffee, water, exercise, or food after drinking. At 0.05 BAC, you need approximately 3.5 hours to reach 0.00. At 0.10 BAC, approximately 7 hours. Sleep does not significantly accelerate elimination.
How many standard drinks is 0.05 BAC?
The relationship between standard drinks and BAC varies significantly by body weight, sex, and food intake. As a very rough guide for a 70kg man after food: approximately 2 standard drinks in the first hour may approach 0.05. For a 60kg woman, 1-2 drinks in the first hour may approach this limit. Individual variation is too high for any rule of thumb to be reliable — the only safe driving limit is zero alcohol.
What is a standard drink in Australia?
One Australian standard drink contains 10g of pure alcohol. This equals: 375mL of 3.5% beer (1 stubby of mid-strength); 100mL of 13% wine (small glass, not a full 150-175mL pour); 30mL of 40% spirits (one nip). Many restaurant wine pours and craft beers contain 1.5-2 standard drinks per serve.
How accurate is a BAC calculator?
A BAC calculator gives only a rough estimate. Real blood alcohol depends on many personal factors — body composition, food, hydration, medications, liver health and genetics — that a formula cannot capture. Two people drinking the same amount can have very different BAC. Never rely on a calculator to judge whether you are safe or legal to drive.
Can I drive after one drink?
Even one drink can impair judgement, reaction time and coordination, and some drivers (learners, professionals, under-age) must have zero alcohol. Because effects and legal limits vary, the safest choice is simply not to drive after drinking any alcohol. Plan a lift, taxi, rideshare or public transport instead.
How many drinks reach 0.05 BAC?
It varies far too much between people to give a safe number — body weight, sex, food, time and metabolism all change the result. Using drink counts to "stay under" a limit is unreliable and risky. The only safe approach is not to drive after drinking, rather than trying to estimate a drink count.
How long until alcohol leaves my body?
Your body clears roughly one standard drink per hour, but this varies by person. If you drink several drinks, it can take many hours to return to zero — often longer than people expect, including the next morning. Only time lowers your BAC; nothing can speed it up.
Does coffee or a cold shower lower BAC?
No. Coffee, cold showers, cold air, exercise and drinking water can make you feel more awake, but they do not remove alcohol from your blood. Your BAC falls only as your liver processes alcohol over time. Feeling more alert while still impaired is especially dangerous.
Do women reach a higher BAC than men?
Often, yes. On average women have a higher proportion of body fat and less body water, so the same amount of alcohol becomes more concentrated in the blood. Hormonal factors can also play a role. This is why BAC formulas use different constants for men and women — but individual variation is still large.
What BAC level is dangerous?
BAC around 0.30% and above can cause confusion, vomiting, loss of consciousness and life-threatening alcohol poisoning. But danger begins much lower — driving ability is impaired from very low levels. If someone is confused, vomiting, breathing slowly or cannot be woken after drinking, treat it as an emergency and call for medical help immediately.