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Morning after calculator

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

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.

Enter a few details to see when it's safe to drive after drinking

What is your birth sex?
Why do we ask this question?
What is your weight? Please select your preferred option
How much did you drink last night?
What time did you stop drinking?

What are the UK drink-drive limits?

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

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.

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

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

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.

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?

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 drunk driving.

How does this calculator work?

The Confused.com morning after calculator estimates your blood alcohol content (BAC) using the Widmark Formula, which is: (Grams of alcohol / [body weight in grams * gender constant])*100

Grams of alcohol are worked out based on units of standard drinks:

  • Pint of 4% beer/cider = 2.3 units
  • Regular glass of 12% wine = 2.1 units
  • Single measure of 40% spirit = 1 unit

Our calculation of ‘time until alcohol-free’ is a conservative estimate of 1 hour per unit of alcohol consumed, plus an extra hour for the first drink to get into your system.

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