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How Many Units Can You Drink And Drive? - Money Expert

Last updated: 24/07/2024 | Estimated Reading Time: 8 minutes

According to the UK Government website, it’s estimated around 280 deaths in 2019 were caused by drivers being over the drink driving limit. But what is the limit?

When you drink, your brain takes longer – and finds it more challenging – to process the information it sees. This slows your body’s reactions.

In the UK, we have legal limits, but you may find you’re unsafe to drive before you reach this threshold. This guide will explain what the legal alcohol limit for drivers in the UK is, and what being over the limit could mean for your insurance premiums.

In This Guide:

What is a unit of alcohol?

Alcohol limits are scientifically measured in micrograms and milligrams, but what this means in real terms can be a little hard to decipher (or should we say digest?). So, in general speak, alcohol limits are broken down into comprehensible bite-size units called… units.

One unit of alcohol is measured as 8mg or 10ml of pure alcohol.

Units are a way of determining the amount of alcohol you’re consuming, however we should stress that these should be taken as a rough guide only. Why? Because there’s no one-size-fits-all when it comes to units, as alcohol affects everyone differently. Let’s take a look at why.

How many units can I drink and drive legally in the UK?

Your sex, weight, age, diet, and critically your metabolism, all play a part in how you process alcohol, as do factors like stress. That’s why some people feel safe to drive after two pints, and others can’t after one.

As a general benchmark though, adults process, on average, one unit of alcohol per hour. Here’s a practical example:

  • A single shot of spirits equates to one unit of alcohol. Therefore, you would need to wait at least one hour before driving.

However, the alcohol levels in your bloodstream can continue to rise for up to three hours after, depending on the variables above. That’s why it’s so challenging to determine your personal drink driving limit, and why the advice is always: if you plan to drink, don’t drive.

In England, Wales and Northern Ireland

Where you live in the UK will also impact how many units you can legally drink and drive.

In England, Wales and Northern Ireland, the current driving limit is approximately three units for women and four units for men.

If you’re looking for the hard stats though – which is what you’re legally tested on - then we’ve broken this down into measurements of three components: breath, blood and urine.

  • 35 micrograms per 100 millilitres(ml) of breath
  • 80 milligrams (mg) per 100ml of blood
  • 107mg per 100ml of urine.

In Scotland

If you’re north of the border, you’ll face stricter limits, which were introduced in 2014. In Scotland, your main driving limit will be:

  • 22 micrograms per 100ml of breath
  • 50mg per 100ml of blood
  • 67mg per 100ml of urine

As a result, the number of units both men and women can drive on is also lower.

How Long After Drinking Can You Drive?

There is no set time limit that means it’s safe for you to drive after drinking alcohol. Because everyone reacts differently to alcohol, it can be difficult to know how long it will be before it leaves your system. The length of time you need to wait until you’re completely sober can also depend on the amount and type of alcohol you drank, so your waiting period may be different every time you drink.

In general, you can expect a unit of alcohol to take around an hour to be processed by your body, but this isn’t always the case. To be extra safe, it’s best to leave 12 to 24 hours between the time you finish drinking and the time you drive, especially if you drank a lot of alcohol.

What Happens If You’re Found Drinking and Driving?

If you’re stopped by the police and they suspect you may have been drinking, they may request that you take a breathalyser test. Refusing the comply with the test can lead to arrest, while failing the test will mean having to take another test at a police station. If you’re still found to have too much alcohol in your system, you’ll face charges.

These charges can vary, but you may receive an unlimited fine or face imprisonment depending on whether you committed any driving offences while under the influence of alcohol. You could also face a driving ban for a varying amount of time.


How many units of alcohol are in a pint of beer?

ABV means alcohol by volume, which is the percentage (%) you see on alcoholic drinks.

A standard 4% lager has 2.3 units, but if you were to opt for a tasty 5.2% craft beer, you’d be consuming 3 units.

How many units of alcohol are in a glass of wine?

Let’s look at a standard bottle of wine, which has a typical ABV of 13%.

A standard glass of wine is 2.3 units, whereas a large glass is 3.3 units

How to work out how many units are in a drink

For the more calculated, there is a formula you can follow:

ABV (%) x volume of drink (ml) ÷ 1000

While this is a good guide to working out units, it doesn’t necessarily reflect your main driving limit, because everyone absorbs alcohol differently. Legal limits act well as guidelines, but only you know yours.

How much can I drink the night before driving?

When people ask how many units can you drink the night before driving, again it is a personal, variable limit. It’s a myth that a cup of coffee, a cold shower or even sleep can reduce the amount of alcohol in your body, because alcohol absorption is a metabolic process.

Having 10 single shots would take 10 hours to process, but remember alcohol levels in your blood can continue to rise for several hours afterwards. And if you’ve been out until 2am after a stressful week at work, having forgone a carb-heavy dinner, it’ll stay in your body even longer.

This is what you need to assess when determining your main driving limit. If you’re in any doubt, one option could be to purchase a breathalyser to confirm whether you are safe to drive the next day.

How to Avoid Drink Driving

While being aware of drink drive limits can help you to avoid drink driving, it’s far safer to avoid alcohol altogether if you’re planning on driving. This means that on days you’re going to be drinking alcohol, you need to make sure you’re aware of alternative transport options, so look up bus schedules or save taxi numbers head of time. Alternatively, if you’re going to be with friends or family, you may decide to nominate a designated driver to take everyone home later.

If you didn’t plan to drink and end up consuming alcohol, it’s important not to drive home if you’re feeling at all uncertain about how much you drank. It’s always best to make alternative arrangements, no matter how inconvenient, rather than risk getting behind the wheel when there’s too much alcohol in your system.

How does drink driving affect car insurance premiums?

If you’re convicted of a drink driving offence, then you’ll find it difficult to get cheap car insurance. Fortunately though, specialist convicted driving insurance policies are a pathway to helping those with a conviction get a premium – and we can help you there! Use our car insurance comparison tool to find a quote that meets your needs.


Is it OK to drive the morning after a night of drinking?

A lot of people assume that going to sleep after a night of drinking will mean they’re fit the drive in the morning, but that’s not always the case. If you’ve only had a drink or two, you’re more likely to be safe to drive, but if you drank a lot, you may still be over the drink drive limit for the entire day.

Can I sleep in my car after drinking?

It’s a bad idea to sleep or sit in your car after drinking alcohol, as if the police catch you, you can still be charged with being drunk in charge of a vehicle. You can be charged with this offence regardless of whether you were planning to drive or not, simply being in a car with the keys while over the legal alcohol limit is an offence.

How many units can a woman drink and drive?

Women can usually drink around 3 units of alcohol before being over the legal limit to drive. However, it’s always best to be cautious and stay well under the limit or avoid drinking at all before driving.

How common is drinking and driving?

Around 85,000 drivers are convicted due to drunk driving every year in the UK.


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