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Morning after calculator

The morning after: when is it safe to drive after drinking?

Do you know how long alcohol stays in your system after drinking? Use our calculator to work out your blood alcohol content. Please note that this may not be accurate as people’s bodies process alcohol differently.

Even though you may have stopped drinking the night before, alcohol can remain in your blood for 6 hours and on your breath for up to 24 hours. You might feel okay to drive, but if the police pulled you over then you could be prosecuted for drink driving.

Our morning after calculator can help you estimate whether you may still be over the drink-drive limit.

Please don’t use our morning after calculator in the place of sensible caution. If you’re drinking, don’t drive. If you’re driving, don’t drink.

What are the UK drink-drive limits?

The drink-drive limit is lower in Scotland than in other parts of the UK1:

Country Micrograms of alcohol per 100 ml breath Milligrammes of alcohol per 100 ml blood Milligrammes of alcohol per 100 ml urine
England, Wales and Northern Ireland
35
80
107
Scotland
22
50
67

1. Drink drive limit data taken from gov.uk on 5th May 2022

For blood alcohol content (BAC) you might see this written as 0.8 mg/ml for England, Wales and Northern Ireland, and 0.5 mg/ml for Scotland.

No blood alcohol calculator is 100% accurate, as a number of factors will affect how your body processes alcohol. Use the tool for reference purposes only. You shouldn’t use it to determine whether you’re fit to drive. We can’t emphasise this enough, if in doubt, do not drive.

Need more help?

When can I drive after drinking?

This depends on a few things, including:

  • How much you weigh
  • How much you've had to drink
  • When you started drinking.

Using our calculator can give you an idea of how much alcohol might be left in your system but it’s not an alcohol unit calculator nor should it be used in place of sensible caution.

How long does it take for alcohol to leave my system?

Medical studies suggest that on average, the body removes alcohol at the rate of about one unit per hour. This is an average though, so how your own body processes alcohol will differ.

Our morning after calculator uses an estimate of 1 hour per unit of alcohol consumed, plus an extra hour for the first drink to get into your system.

Also, despite the myths, there’s no way to speed up the process. Drinking coffee or taking a cold shower might make you feel different, but it won’t lower the amount of alcohol in your system.

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