Blood Alcohol Concentration (BAC) is a critical measure used in Australia to determine the level of alcohol intoxication in a person’s bloodstream. It is expressed as the amount of alcohol (in grams) per 100 millilitres of blood. For example, a BAC of 0.05% means there is 0.05 grams of alcohol in every 100 mL of blood. This measurement is central to Australia’s drink-driving laws and safety guidelines. This blog post explains the BAC chart, what different BAC levels mean, and how they relate to your behaviour and legal limits.
What Is BAC?
BAC quantifies the concentration of alcohol in your blood and is used to assess impairment. Police use breath tests or blood tests to measure BAC, especially during roadside checks. In Australia, the general legal limit for fully licensed drivers is 0.05% BAC, though some drivers must maintain a zero BAC depending on their licence type.
How Does Alcohol Affect BAC?
After consuming alcohol, it is absorbed into the bloodstream through the stomach and small intestine. The liver metabolises alcohol at an average rate of about 0.01% BAC per hour, roughly equivalent to processing one standard drink per hour. However, many factors influence BAC, including body weight, gender, metabolism, drinking speed, and whether you’ve eaten.
BAC Chart: Effects of Different BAC Levels
Here’s a simplified guide to what different BAC levels typically mean in terms of effects on the body and behaviour:
| BAC Level (%) | Likely Effects |
|---|---|
| 0.00 – 0.02 | Minimal or no impairment; slight relaxation or mild mood changes. |
| 0.02 – 0.05 | Mild euphoria, lowered inhibitions, slight impairment in judgment and coordination. |
| 0.05 – 0.08 | Noticeable impairment of judgment, slower reaction times, reduced coordination; increased accident risk. |
| 0.08 – 0.15 | Significant impairment: slurred speech, poor balance, blurred vision, impaired perception. |
| 0.15 – 0.30 | Severe impairment: difficulty walking, extreme drowsiness, vomiting, memory blackouts. |
| Above 0.30 | Life-threatening: loss of consciousness, slowed breathing, risk of alcohol poisoning. |
Legal BAC Limits in Australia
- General drivers: Must keep BAC below 0.05%.
- Learner and provisional drivers: Must maintain a zero BAC (0.00%).
- Commercial drivers and certain professional drivers: Often required to have zero BAC.
- Penalties: Exceeding legal limits can lead to fines, licence suspension, or imprisonment.
How Many Drinks Affect Your BAC?
One standard drink in Australia contains 10 grams of pure alcohol. On average, one standard drink raises BAC by approximately 0.01% to 0.03%, but this varies widely. For example, an average adult male might reach the 0.05% limit after about 2–3 standard drinks consumed over an hour, while women or lighter individuals may reach it sooner.
Understanding the BAC chart helps Australians make informed decisions about alcohol consumption and driving. Since BAC levels directly impact your coordination, judgment, and legal standing, it’s essential to know your limits and drink responsibly. The safest choice is always to avoid driving if you have consumed any alcohol.