Many people who drink alcohol and drive ask the same question: How many standard drinks, beers, pints or glasses of wine can I have before I am over the legal limit?
There is no reliable number that can guarantee you will remain under the legal blood alcohol concentration (BAC) limit.
Your BAC depends on a range of factors, including how much alcohol you consume, how quickly you drink, your body size, whether you have eaten, your metabolism and the time that has passed since you stopped drinking.
For this reason, NSW authorities advise that the safest way to ensure you are under the legal limit is not to drink alcohol if you intend to drive.
Read more about different types of drink driving offences here.
What is a standard drink?
In Australia, a standard drink contains 10 grams of alcohol. A standard drink is not necessarily the same thing as one beer, one glass of wine or one shot of spirits.
The number of standard drinks in a beverage depends on the drink’s alcohol content and serving size.
For example, a large glass of wine can contain considerably more than one standard drink, while a pint of full-strength beer can also contain more than one standard drink. This is one reason why simply counting the number of drinks you have consumed can give you a false sense of security.
How many standard drinks are in a beer?
The number of standard drinks in a beer depends on its size and alcohol content. For example, a full-strength beer may contain about 1.4 standard drinks in a typical 375 mL serving, although the exact amount varies between products.
A larger beer or pint can contain significantly more.
The alcohol percentage printed on the bottle, can or menu is therefore important when working out how many standard drinks a particular beer contains.
What about a pint?
A pint is a measure of volume, not a standard drink.
A pint can therefore contain different amounts of alcohol depending on:
- The size of the pint being served,
- The beer’s alcohol percentage, and
- Whether the beer is full-strength, mid-strength or low-strength.
A pint of full-strength beer can contain considerably more than one standard drink.
How many standard drinks are in a glass of wine?
Wine also varies significantly.
The number of standard drinks depends on:
- The size of the glass,
- The alcohol percentage of the wine, and
- How full the glass is.
A small 100 mL glass of wine at around 12% alcohol is approximately one standard drink. A 150 mL restraint pour can contain 1.4 standard drinks.
A large class can contain substantially more.
How many standard drinks can I have and still drive in NSW?
For fully licensed drivers in NSW, the BAC limit is 0.05 or lower.
Learner and provisional drivers must have a BAC of 0. Certain professional and heavy vehicle drivers are also subject to a limit below 0.02.
There is no fixed number of standard drinks that will guarantee a driver remains under 0.05.
An old rule of thumb suggests that an average man may have two standard drinks in the first hour and one standard drink per hour thereafter, while an average woman may have one standard drink per hour and remain below 0.05 BAC. However, this should not be relied upon as a reliable measure of whether you are legally safe to drive. BAC varies between individuals, and you can still exceed the legal limit even if you follow these guidelines.
How long does alcohol stay in your system?
Alcohol takes time to leave your body. The only reliable way for your BAC to fall is for your body to metabolise the alcohol over time. This is particularly important the morning after drinking.
You may feel completely sober but still have alcohol in your system. If you drank heavily the night before, assuming that you are safe to drive simply because you have slept is not a reliable way of determining your BAC.
If you are unsure whether you are still affected by alcohol, the safest option is not to drive.