How much can I drink and drive?

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.

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.

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.

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.

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.

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.