How many drinks can you have and drive?

Drink driving laws and legal limits in Perth, Western Australia.
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    In Perth, it’s pretty hard to get around without a car! So understandably, you may be wondering how many standard drinks you can have and drive?

    The answer isn’t really straightforward, as various factors influence your ability to drive safely after consuming alcohol. Questions like “how long after drinking can I drive?” and “how long after drinking can I drive?” are common, but before answering, it’s important to take into careful consideration of personal tolerance, legal limits, and the type of drinks consumed.

    In this article, we’ll explore the complexities behind how many drinks you can have and drive, and provide insights to help you make responsible decisions. Remember, drink driving is a serious offence with severe legal, financial, and health consequences. Understanding these factors is crucial for ensuring your safety and the safety of others on the road.

    The laws in Western Australia surrounding drink driving

    Any alcohol at all will affect your ability to drive. Unless you want to risk having to make friends with a Perth drink driving lawyer, it’s important to be aware of the current laws in WA surrounding drink driving.

    According to WA Police, it is an offence to drive while your blood alcohol concentration (BAC) is 0.05 or above. To stay within the legal limit, your BAC should remain below 0.05 if you follow these guidelines:

    • For men of average size: drink no more than two standard drinks in the first hour and one per hour thereafter.
    • For women of average size: drink no more than one standard drink per hour.

    These guidelines are general and individual variations in tolerance and metabolism can affect BAC. The safest choice is always to avoid drinking if you plan to drive.

    There are exceptions to this rule when it comes to how many drinks you can have and drive

    Like with most things in life, there are exceptions to these rules. Your BAC must be 0 (meaning you can’t drink and drive at all) if the following circumstances apply to you:

    • You do not have a full Western Australian driver’s licence (E.g you are on your L or P plates).
    • You have an extraordinary driver’s licence (E plates).
    • You have recently been disqualified for certain alcohol or drug related offences.
    • You are driving:
      • A bus (defined as vehicles seating more than 12 adults).
      • A vehicle carrying passengers for a reward or hire purposes (e.g Rideshare drivers or taxi drivers).
      • A vehicle transporting dangerous goods.
      • A vehicle with a GCM (gross combination mass) of or greater than 22.5t.

    What is a standard drink?

    When determining how many drinks you can have and drive, most laws refer to this in standard drinks. A standard drink is a measure used to quantify the amount of pure alcohol in a beverage. It provides a way to compare the alcohol content across different types of alcoholic drinks and helps individuals understand how much alcohol they are consuming.

    The concept of a standard drink varies slightly between countries, but it typically represents a specific amount of pure alcohol. In Australia, a standard drink contains 10 grams of pure alcohol or 12.5ml.

    How do you calculate a standard drink?

    To calculate a standard drink, multiply the volume of the beverage (in litres) by its alcohol by volume (ABV) percentage and then multiply the result by 0.789 (the density of ethanol) to determine the grams of pure alcohol, with one standard drink equalling 10 grams of pure alcohol.

    You can utilise the DrinkWise Standard Drink Calculator to better estimate your alcohol intake.

    How standard drinks are calculated across different alcoholic beverage types

    Here’s a quick summary of common drinks to give you a rough idea.

    • Middy of full strength beer: 285ml, 4.8% = 1.1 standard drinks
    • Pint of full strength beer: 570ml, 4.8% = 2.1 standard drinks
    • Glass of red wine: 150ml, 13% = 1.5 standard drinks
    • Shot of vodka: 30ml, 40% = 1 standard drink


    Key Points to Remember

    • The number of standard drinks in a beverage can vary depending on its size and alcohol content.
    • Always check the label for alcohol content and serving size to accurately calculate the number of standard drinks.

    What else affects BAC levels?

    Now that you understand the laws surrounding BAC when driving and what a standard drink is, it’s important to understand what else determines your BAC levels. Several factors can influence how alcohol affects your body and, consequently, your BAC. These factors include:

    Body weight

    People who weigh more generally have a lower BAC after consuming the same amount of alcohol compared to people who weigh less, as alcohol is distributed throughout the body’s water content.


    Women typically have higher BAC levels than men after consuming the same amount of alcohol due to differences in body composition and metabolism.


    Younger and older individuals may process alcohol differently, with metabolism rates varying across different age groups. For instance, younger adults in their twenties generally have a faster metabolism, allowing their bodies to process and eliminate alcohol more quickly than older adults.


    Individual metabolic rates can affect how quickly alcohol is processed and eliminated from the body. Metabolism refers to the chemical processes that occur within a living being in order to maintain life, including the breakdown of substances such as alcohol. For example, someone with a naturally high metabolic rate will process and eliminate alcohol more quickly than someone with a slower metabolic rate.

    Food intake

    Consuming food before or while drinking can significantly slow the absorption of alcohol into the bloodstream, resulting in a lower BAC. When you eat, your stomach starts digesting the food, and this process can affect how quickly alcohol is absorbed into your bloodstream.

    Type and strength of alcohol

    Different alcoholic beverages contain varying amounts of alcohol. Spirits typically have a higher alcohol concentration compared to beer or wine. Due to their higher concentration, spirits are often absorbed by the body more quickly, leading to a more rapid increase in BAC.

    Rate of consumption

    The way alcohol is consumed also plays a role. Drinking a pint of beer over a meal will generally result in a slower rise in BAC compared to taking multiple shots of vodka in quick succession. The quick consumption of high ABV drinks can overwhelm your body’s ability to metabolise alcohol, leading to higher and faster BAC increases.

    Health conditions and medications

    Certain health conditions and medications can affect how the body processes alcohol. For example, The liver is primarily responsible for metabolising alcohol. Conditions such as cirrhosis, hepatitis, or fatty liver disease impair liver function, slowing down the process of alcohol metabolism. This results in higher BAC levels for a longer duration, increasing the risk of impairment.

    How long after drinking until I can drive legally?

    Determining how long after drinking until you can drive legally depends on the factors mentioned above. As a general rule of thumb, for each standard drink consumed, allow at least one hour before driving.

    For example, if you had five standard drinks starting at 8 PM and finished by 10 PM, you should ideally wait at least five hours from the time of your last drink before considering driving. This means you would not be safe to drive until around 3 AM. However, individual variations in alcohol metabolism can affect this estimate.

    If you are unsure whether you are under the legal limit, it is safest to avoid driving altogether. Consider alternative transportation options such as taxis, ride-sharing services, or public transport.

    Stay safe on the roads by being aware of how many drinks you can have whilst driving

    Understanding how alcohol affects your body and the factors influencing your Blood Alcohol Concentration (BAC) is crucial for making informed and responsible decisions about getting behind the wheel after a night out at the pub with your mates. While methods like the drinks per hour rule and online BAC calculators can provide general guidance, personal breathalysers offer a more accurate assessment of your BAC.

    Remember, the safest choice is always to avoid drinking if you plan to drive. By being aware of the effects of alcohol and the importance of staying within legal limits, you can help ensure your safety and the safety of others on the road.

    This article is not here to encourage drink driving. This is simply trying to provide information about local laws, and make them easier to understand for Perth drivers. Beer Is OK does not condone drink driving and always recommends people drink responsibly. Always organise a designated driver.

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