Blood Alcohol Concentration Calculator
Estimate your BAC
This tool gives a general estimate of your BAC after consuming alcohol. BAC calculators cannot be completely accurate, your actual, BAC may be higher or lower depending on body composition, age, sex, food intake, drinking speed, liver function, medications, fatigue and individual metabolism. The safest option is not to drive after drinking.
Simplified Australian Standard Widmark Formula
- Alcohol in grams: Number of standard drinks x 10 (A standard drink contains roughly 10g of pure alcohol)
- Body Weight in grams: e.g., 75Kg = 75,000gram
- Biological Sex: r= Body Water Distribution Ratio (Males r=0.68, Females r=0.55). These are population averages only. Actual values vary with age, body composition and individual physiology, so the calculator may under- or over-estimate your true BAC.
- (0.015%) refers to rate of alcohol metabolism by the liver per hour. Actual elimination varies between people and may be slower or faster. Do not use this number to decide when it is safe to drive
- Hours elapsed: Hours Since First Drink (How long has it been since you started drinking, in hours?)
Results based on Calculation:
- If BAC = 0.00%: You likely have no alcohol in your system.
- If your BAC is greater than 0.00% but less than 0.05%: Alcohol is present in your system, and driving is not recommended. Learner drivers, P-platers, and professional drivers (such as taxi, bus, and truck drivers) are required to maintain a BAC of 0.00%. Even at levels below 0.05%, alcohol can impair judgement, reaction time, and coordination.
- If BAC is 0.05% or higher: ⚠️ Over the legal 0.05% driving limit. Do not drive.
Quick Facts / Info Grid
Legal Limit
In Australia, a BAC of 0.05% is the strict legal limit for driving a vehicle (varies by license).
Standard Drink
A standard drink contains exactly 10g of pure alcohol, regardless of the beverage size or type.
No Safe Level
The WHO states there is no “safe” level of alcohol consumption that benefits your overall health.
What is the BAC in Australia?
Blood Alcohol Concentration (BAC) refers to the amount or portion of alcohol present in your body’s bloodstream. It is typically measured in grams of alcohol per 100 millilitres of blood.
In Australia, a BAC of 0.05% is the legal limit for driving, depending on the type of licence (e.g., learners and provisional drivers must maintain a 0.00% BAC).
This calculator provides a rough estimate of the amount of alcohol in your bloodstream. It factors in your biological sex, weight, and the number of drinks consumed over a set period to offer an approximate BAC level.
What are the key points about BAC?
- The measurement of BAC is in grams of alcohol per 100 millilitres of blood (g%).
- The upper limit of BAC in Australia is 0.05% for driving. It varies and lowers depending on the licence.
- Factors influencing BAC include (and are not limited to) speed of alcohol consumption, food intake, body weight, liver health, and biological sex.
- Effects of BAC vary from mild effects (relaxation) to serious consequences (like loss of consciousness).
- Alcohol can initially have stimulant effects, but as BAC increases, the depressant effects become more pronounced.
In Australia, driving with a blood alcohol level over 0.05% is illegal. If you plan to drink, it’s important to consider safer transport alternatives such as public transport, rideshare services, or arranging a designated driver to ensure you get home safely.
Examples of BAC levels with meaning
| BAC Level | Potential Effects on the Body |
| 0.00% | There’s no alcohol in your blood (you’re completely sober). |
| 0.02% | Altered mood, relaxation, and a slight loss of judgment. |
| 0.05% (Legal Limit) | Feeling uninhibited, lowered alertness, and impaired judgment. |
| 0.08% | Reduced muscle coordination, difficulty detecting danger, impaired reasoning. |
| 0.10% | Reduced reaction time, slurred speech, and slowed thinking. |
| 0.15% | Altered mood, nausea, vomiting, and loss of balance and some muscle control. |
| 0.15% to 0.30% | Confusion, vomiting, and drowsiness. |
| 0.30% to 0.40% | Likely alcohol poisoning, loss of consciousness. |
| Over 0.40% | Critical risk of coma and death due to respiratory arrest (absence of breathing). |
What does the BAC calculation mean?
There’s no guarantee that staying below a certain number of drinks will ensure your BAC remains below 0.05. Do not use drink-count rules or this calculator to decide whether to drive. If you plan to drive, it’s always best to avoid alcohol altogether.
- A BAC of 0.05%: It is often reached after approximately 2 standard drinks for men and 1 standard drink for women in the first hour, followed by about 1 standard drink per hour thereafter. However, BAC is affected by many factors, including sex, body weight, food intake, age, metabolism, and overall health. As a result, there is no reliable number of drinks that can guarantee you will remain below the legal driving limit.
- 0.05 – 0.08 g% BAC: It is likely to put you at risk. Effects include impaired judgment and low inhibitions.
- 0.08 – 0.15 g% BAC: It is a risky state. Effects include unstable emotions, nausea, vomiting and slurred speech.
- 0.20 – 0.29 g% BAC: It is generally a feeling of confusion or disorientation, in which you may need help walking. Nausea or vomiting is common at this level.
Alcohol & BAC FAQs
What is meant by a standard drink?
A standard drink is roughly 10g of pure alcohol, according to the Australian Government Department of Health and Aged Care. This volume can vary significantly depending on the beverage type (beer, wine, spirits) and the size of the glass it is served in.
How many drinks is 0.05 for women?
BAC levels vary based on factors like body weight, metabolism, and food intake, so these are just guidelines. However, for an average-sized woman, consuming one or two standard drinks within a 1 to 2 hour period could reach a Blood Alcohol Concentration (BAC) of 0.05%.
How many standard drinks would I drink before I reach 0.05?
There is no standard rule of thumb as it depends on many factors. Your age, food consumed, rate of consumption, biological sex, metabolism, underlying health conditions (like liver function), medications, and fat-to-muscle ratio all dictate how quickly you reach 0.05.
Does urinating lower BAC?
No, urinating does not lower your Blood Alcohol Content (BAC). Alcohol is primarily metabolised by the liver, and only a very small percentage is eliminated through urine, sweat, and breath. The amount eliminated through urine is negligible, meaning urinating will not sober you up.
What alcohol level is too high?
Determining when your blood alcohol level is too high depends on the context. Staying under the legal limits doesn’t necessarily mean it’s safe to drive. Any amount of alcohol is “too much” if you are pregnant, managing chronic health conditions, or taking medications. In terms of strict clinical toxicity, a blood alcohol concentration (BAC) over 0.40% is highly life-threatening and can lead to respiratory depression, coma, or death.
What BAC level is good for you?
No amount of alcohol is inherently “good” for your health. According to the World Health Organization (WHO), “safe” alcohol consumption doesn’t mean there are health benefits. While a glass of wine may have trace antioxidants, the benefits do not outweigh the negative impacts of alcohol on the body.
How is BAC measured?
Blood alcohol concentration can be accurately measured on the spot with a police breathalyser, or in a clinical setting by analysing a sample of your blood.
Can I get medical advice late at night for BAC or alcohol symptoms?
Yes, with Hola Health, you can get medical advice 24/7 – even late at night. Our Australian-registered practitioners are available anytime via secure telehealth consultations to guide you on general symptoms like mild nausea or hangover. Please note: Telehealth is not suitable for acute alcohol intoxication or poisoning. If someone is unresponsive, confused, or vomiting continuously, call 000 immediately.
Disclaimer: This calculator provides a general BAC estimate only. It cannot account for individual factors like food intake, metabolism, or exact body composition. Never use this tool to decide if it is safe or legal to drive. The only way to guarantee you remain under the legal limit is to avoid alcohol altogether.
This content is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Do not delay seeking medical care based on information read here. In emergencies (such as suspected alcohol poisoning), call 000 immediately. Assessment of alcohol-related symptoms via telehealth is limited to non-emergencies (e.g., mild hangover symptoms). The issuance of prescriptions and medical certificates is at the strict clinical discretion of the consulting practitioner and is never guaranteed. Ensure your privacy is protected. All consultations are strictly confidential and conducted via secure, encrypted platforms to safeguard your personal health data.
- Australian Standard Drink Definition (10g of pure alcohol) – Source: Australian Government Department of Health and Aged Care: https://www.health.gov.au/topics/alcohol/about-alcohol/standard-drinks-guide
- Australian Legal BAC Limit for Driving (0.05%) – Source: Australian Government Department of Health / State Transport Authorities: https://www.health.gov.au/topics/alcohol/about-alcohol/alcohol-laws-in-australia
- No “Safe” Level of Alcohol Consumption – Source: World Health Organization (WHO): https://www.who.int/europe/news/item/04-01-2023-no-level-of-alcohol-consumption-is-safe-for-our-health
- BAC Calculation Formula (Widmark Equation usage in Australia) – Source: Australian Institute of Criminology / Australian Transport Accident Commission (TAC) research: https://www.aic.gov.au/sites/default/files/2020-10/proceedings1.pdf
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