News and Events

What is the Drinking limit?

  • Posted

Anyone who is driving, attempting to drive, or in charge of a motor vehicle, whether it be on the road or in a public place.

for example a pub car park or a garage forecourt, may be required by the police to provide a breath test, in order to check that they are under the prescribed limit of alcohol. Depending on circumstances, you may be also required to take a blood or urine test.

Breath test limit
35 micrograms of alcohol per 100 millilitres of breath (22 micrograms in Scotland)

Urine test limit
107 milligrams of alcohol per 100 millilitres of urine (67 milligrams in Scotland)

Blood test limit
80 milligrams of alcohol in 100 millilitres of blood (50 milligrams in Scotland)

What constitutes a unit of alcohol?
One unit of alcohol is 10ml (1cl) by volume or 8g by weight, of pure alcohol.

How do I calculate how many units there are in a drink?
A unit of alcohol is measured by the size (ml) and strength (% alcohol by volume or ABV) of the drink.

The following is a guideline:


Small Glass (125ml)
12% - 1.5 units
14% - 1.75 units
Standard Glass (175ml)
12% - 2.1 Units
14% - 2.45 Units


Half Pint
3% - 1 Unit
4% -  1.1 Units
5% - 1.4 Units
330 ml Bottle
3% - 1 Unit
4% - 1.1 Units
5% - 1.7 Units
1 Pint
3% - 2 Units
4% - 2.2 Units
5% - 2.8 Units


Single Shot (25ml)
40% - 1 Unit
Double Shot (50 ml)
40% - 2 Units

Port 20% - single shot is 0.5 Unit; double shot is 1 Unit

What to do if you are caught driving over the limit?
You will be taken into police custody and your vehicle may be impounded. Try to remain calm and consult a solicitor. If you have been caught drink driving, we have all the information you will need to know that could help reduce your fine and help protect your licence.

Please get in contact with us on our 24hour hotline 02077379339 or request us while you are in police custody