Blood alcohol concentration limits

What is blood alcohol concentration or BAC?

Blood alcohol concentration (BAC) is the measurement of the number of grams of alcohol in 100ml of blood. Drink driving offences are described according to the BAC level at the time of driving. For example, there is an offence of driving with a BAC of 0.05 and up to 0.08, and another offence of driving with a BAC of 0.08 and up to 0.15. 

What are the BAC limits for driving?

Your BAC limit for driving depends on the type of driver's licence or permit you have and the status of your licence. Most people are subject to a 0.05 BAC limit, although some people are subject to a 0.00 BAC limit.

Who is subject to a 0.00 BAC limit?

A 0.00 BAC limit means it is an offence to drive with any amount of alcohol in your body.. There are many examples of people who are subject to a 0.00 BAC limit including:

• Novice drivers
• Drivers who have been convicted of an alcohol interlock offence
• Heavy vehicle drivers
• Drivers of vehicles carrying dangerous goods
• Taxi drivers, who are carrying passengers for hire or reward.

There is full information about who is subject to a 0.00 BAC limit, including who is a novice driver, in the Legal Aid WA Infosheet - Traffic - Part 2: Common offences and penalties, under the heading 'Drink driving offences'.

Who is subject to a 0.05 BAC limit?

Every driver who is not subject to a 0.00 BAC limit, is subject to a 0.05 BAC limit. Therefore, it is an offence for anyone to drive with a BAC at or above 0.05. 

What penalty can I get for driving over my BAC limit?

The penalty you can get will depend on the offence, which depends on your BAC at the time of driving. The higher the BAC the more serious the offence and the higher the penalty. 

There are a range of different penalties a court might give you for a drink driving offence. The most common penalty is a fine and disqualification from driving for period of time. Your licence might also be automatically cancelled. For some serious drink driving offences you can be sent to prison.

If you are stopped by police for an excess 0.08 or DUI (excess 0.15) offence, you will normally be given a roadside disqualification notice, which stops you from driving for 2 months. If you are then convicted of the offence in court you can be given more disqualification time, but the court will take into account the time you have already been disqualified under the roadside notice. 

For some offences you might also be subject to the Alcohol Interlock Scheme.  This means you must meet certain requirements from the Department of Transport before you can apply to drive again.

There is full information about the penalties that you can be given by a court for particular drink driving offences in the Legal Aid WA Infosheet - Traffic - Part 2: Common offences and penalties, under the heading 'Drink driving offences'. The Infosheet - Traffic - Part 1: How to deal with your traffic offence has general information about the different types of penalty that might be given by a court.

Resources from Legal Aid WA

• Infosheet - Traffic - Part 1: How to deal with your traffic offence

• Infosheet - Traffic - Part 2: Common offences and penalties

More information

Department of Transport

• Driving offences (speeding, alcohol and traffic)
• Roadside disqualification notice (Immediate disqualification notice)
• Alcohol Interlock Scheme

Road Safety Commission

• Road rules and penalties - Drink and drug driving

Last reviewed: 9 September 2026