Drink-driving limits - are you unintentionally breaking the law?

Drink-driving limits - are you unintentionally breaking the law?

In the UK, 18 per cent of drink drivers are caught after wrongly assuming they are under the limit after drinking alcohol the night before.

Alcosense has revealed four pints the previous night could mean a driver is legally over the limit until as late as 2pm the next day.

Even more worryingly, research shows over half of UK drivers have unintentionally driven while being over the limit after drinking the night before.

With one in six deaths on the road involving drivers over the legal limit and a maximum penalty of six months in prison and an unlimited fine, it is essential drivers are aware of the risks of driving.

As little as three pints of beer or three large glasses of wine could mean you are over the limit the next day. It could be less, however, as things like having a cold can slow the process of absorbing the alcohol and keep a driver over the limit for longer.

In response to the figures, and with the number of drink driving convictions expected to increase during the football World Cup in June and July, we’ve gathered together some advice on avoiding unintentionally drink driving.

The legal drink-drive limit

Officially, the legal limit in the UK is 80 milligrammes of alcohol in 100 millilitres of blood. This is known as the blood alcohol concentration (BAC).

There have recently been calls to lower the limit to 70 milligrammes, but there are no plans to do this yet.

The problems

The drink-drive limit raises problems for people who believe certain urban myths. The amount of alcohol in a drink is measured in units. For example, 10 millilitres of pure alcohol is equivalent to one unit.

However, it is impossible to calculate if you are under the limit by simply counting units. Alcohol levels can be affected by a large number of things, including:

  1. Your size and weight: It is possible to be more affected by alcohol if you are smaller and lighter.
  2. Your sex: Women are generally smaller and therefore have less water and fat than men.
  3. Your water level: The more dehydrated you are, the greater the effects of alcohol.
  4. Your food intake: Drinking on an empty stomach increases the effect of alcohol.
  5. What you drink: Spirits and stronger drinks will be absorbed more quickly.


It is wrong to assume the traditional myth two pints of beer or two small glasses of wine will result in somebody being under the alcohol limit.

As a rough guide, one unit of alcohol is equivalent to a small glass of nine per cent wine, a 25ml of 40 per cent spirit or half a pint of 3.5 per cent ABV lager, beer or cider.
However, this is a very rough guide. In UK pubs, it is much more likely to be served larger glasses of wine and stronger lager - sometimes closer to five per cent ABV.

Alcohol content of some popular drinks

  1. A pint of ordinary strength lager (Carling Black Label, Fosters) - 2 units
  2. A pint of strong lager (Stella Artois, Kronenbourg 1664) - 3 units
  3. A pint of ordinary bitter (John Smith’s, Boddingtons) - 2 units
  4. A pint of best bitter (Fuller’s ESB, Young’s Special) - 3 units
  5. A pint of ordinary strength cider (Woodpecker) - 2 units
  6. A pint of strong cider (Dry Blackthorn, Strongbow) - 3 units
  7. A 175ml glass of red or white wine - around 2 units
  8. A pub measure of spirits - around 1 unit
  9. An alcopop (e.g. Smirnoff Ice, Bacardi Breezer, WKD, Reef) - around 1.5 units

Could you be unintentionally over the limit?

According to Alcosense:

Allow at least 1 hour for every unit of alcohol you drink to pass through your body before you drive but ideally 1.2 hour per unit. Your pub will be able to tell you how many units are in your drink but a main brand pint of beer will have anything between 2 units *(Fosters) and 3 units *(Stella) .
Calculate the time like this:

Units consumed x 1 hour = hours until I’m clear
So if I drank 4 pints of Stella it would be: 4 pints x 3 units x 1 hour = 12 hours
If I stopped drinking at midnight, I would only just clear the alcohol from my system by 2pm the next day!

The effects

Alcohol lowers inhibitions and makes you feel reckless, affects physical co-ordination and reaction times and affects your judgement. This can be particularly dangerous when driving.

The minimum sentence for being caught drink driving - even the morning after the night before - is a 12 month driving ban. It can result in a prison sentence and a hefty fine. There are other consequences as detailed below:

  1. A criminal record
  2. A minimum 12 months driving ban or a minimum of a 3 year driving ban if you have a previous drink driving conviction in the past 10 years
  3. The possibility of a short spell in prison (up to 6 months)
  4. The possibility of receiving a community order (this can include, unpaid work, curfew, supervision and treatment orders)
  5. The possibility of a hefty fine (up to £5000)
  6. The possibility of losing your job
  7. Your lifestyle could change drastically
  8. Your motor car insurance premiums will be higher once you get your licence back