Clarity Law

Specialist Traffic Law Firm Queensland
Thursday, 05 November 2015 11:30

Why the rule of thumb should not be relied on

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Here at Clarity Law we receive enquiries every day from people who have been charged with drink driving in Queensland even though they carefully monitored their alcohol consumption and the time in which did so. Your BAC (breath alcohol concentration) is the measurement of the amount of alcohol in your blood stream. The legal limit in Queensland, for an open licence driver, is 0.05. This means your body can contain 50 milligrams of alcohol per 100 millilitres of blood.  

What your legal BAC is depends on the class of licence you have. Learners and probationary licence holders have a no alcohol limit which open C class drivers have to be 0.05 or under. For more information on this see –

Whilst it is commonly thought that the rule of thumb is two standard drinks in the first hour and then one every hour after that for men and one standard drink in the first hour and then one every hour after that for woman this is more often than not inaccurate. This is simply a guideline put out by the authorities and should by no means be relied upon and is not a defence in a Court. As soon as you start drinking your BAC goes up. It takes, on average, 30-60 minutes after you finish drinking for your BAC to reach its peak.

People also forget that there are other factors that might influence your BAC reading;

  • 1.       Is your drink actually a standard serve? Most pre-bottled beers and spirit cans, and wine glasses etc are more than 1 standard drink. In Australia a standard drink refers to 10 grams of alcohol (which is equivalent to 12.5milligrams of pure alcohol).   Listed below is the guide to some popular drinks;

Can of low-strength beer = 0.8 standard drink
Can of mid-strength beer = 1 standard drink
Can of full-strength beer = 1.4 standard drinks
100ml wine (13.5% alcohol) = 1 standard drink

150ml wine (13.5% alcohol) = 1.5 standard drinks (average restaurant serving)
30ml spirits = 1 standard drink

Can of pre mixed spirits (approx. 5% alcohol) = 1.2-1.7 standard drinks
Can of pre mixed spirits (approx. 7% alcohol) = 1.6-2.4 standard drinks

  • 2.       How long have you waited since you finished your last drink?
  • 3.       Have you consumed an adequate amount of food that day? This is a big one. The majority of our clients are surprised when they find their reading was over the legal limit and find it was more than likely caused by the lack of food they had consumed that day.
  • 4.       Your body size and how often you consume alcohol can also come into it effect.
  • 5.       Your health – are you healthy, do you have a liver condition, are you feeling sick or stressed?
  • 6.       Are you on medication that may increase the effects or the way that your body processes alcohol? Whilst this is not a defence in Court, as regardless of whether you knew the medication may affect your alcohol levels, the end conclusion is that you were driving with an alcohol level above the legal limit.

Many people think that consuming water, coffee, food etc after consuming alcohol will assist in bringing down their alcohol level. Unfortunately, the only thing that will bring your alcohol level down is time.

Queensland has some of the harshest penalties for drink drivers in both fines and suspension periods.   It is critical to get good advice about the charge and whether you might be able to apply for a work licence.  Information on applying for a work licence can be found on work licence page

Here at Clarity Law we represent drink driving charges in Courts across South East Queensland every day, it is this experience, and our expertise that allows us to get the absolute best result for clients.  Other law firms simply don’t have the experience that we do and don’t know the process and the Magistrates like we do.  We also offer the most competitive prices in Queensland that are all fixed fee so there are no nasty surprises when you receive your invoice.  If you want to engage us or just need further information or advice then you can either;

For more information visit our drink driving page or call 1300 952 255 7am – 7pm seven days a week


Disclaimer – this article contains general advice only and is not intended to be a substitute for legal advice.  We are also not health professionals and our observations on drink driving and what effects a person’s BAC reading is based on our knowledge of representing thousands of drink driving client’s overs the past 15 years and not any specific medical training.  Every state has different laws and information in this article refers to Queensland law only.

Last modified on Friday, 06 November 2015 15:40
Belinda Smyth

Belinda has been with Clarity Law since 2010 and has been involved in the legal industry since 2000. | This email address is being protected from spambots. You need JavaScript enabled to view it.