If you’re wondering what the legal limit for drink driving actually is, you’re not alone. Every year, thousands of drivers across England and Wales are stopped, tested, and charged with driving over the limit, often without understanding where that limit sits or how it’s measured.
The legal limit for drink driving is set out in the Road Traffic Act 1988, and it’s measured differently depending on whether police test your breath, blood, or urine. In this guide, our driving offence solicitors explain exactly where that threshold sits, how it’s tested, and what happens if you’re caught over it.
What Is The Legal Limit For Drink Driving In The UK?
Under Section 5 of the Road Traffic Act 1988, it’s a criminal offence to drive, attempt to drive, or be in charge of a vehicle if the alcohol in your system exceeds the legal limit for drink driving. In England, Wales, and Northern Ireland, the drink drive limit is 35 micrograms of alcohol per 100 millilitres of breath, 80 milligrams per 100 millilitres of blood, and 107 milligrams per 100 millilitres of urine.
Scotland applies a stricter blood alcohol limit UK drivers north of the border need to be aware of, with the breath limit set at 22 micrograms and the blood limit at 50 milligrams per 100 millilitres. A driver could be under the drink drive limit in England but over it the moment they cross into Scotland, so it’s worth checking the rules before travelling.
| Sample Type | England, Wales & Northern Ireland | Scotland |
| Breath | 35 micrograms per 100ml | 22 micrograms per 100ml |
| Blood | 80 milligrams per 100ml | 50 milligrams per 100ml |
| Urine | 107 milligrams per 100ml | 67 milligrams per 100ml |
How Is The Drink Drive Limit Measured?
Police typically use a roadside breathalyser for an initial reading. If that reading suggests you’re close to or over the legal alcohol limit, you’ll be taken to a police station for a second, more accurate breath test on an approved evidential device. Officers will sometimes request a blood or urine sample instead, particularly where a breath test isn’t possible or the reading is disputed.
A driver can also be charged with being unfit to drive through drink, even without a precise reading, provided there’s other evidence such as erratic driving, slurred speech, or the smell of alcohol. This charge depends on the overall circumstances of the stop rather than a fixed drink driving law threshold.
Officers don’t need a specific reason to breath test a driver. The police can request a breath sample if you’ve committed a moving traffic offence, been involved in a collision, or if they simply have reasonable suspicion you’ve been drinking.
Is There A Safe Amount To Drink Before Driving?
You may be asking, is there a safe amount of alcohol I can drink and still stay under the legal limit for drink driving? There isn’t a reliable answer, because alcohol affects everyone differently depending on body weight, metabolism, what you’ve eaten, and how well you slept.
Units-based calculators offer a rough guide, but they’re not accurate enough to rely on if you intend to drive. The only genuinely safe approach is not to drink at all before getting behind the wheel.
How Many Units Can You Drink Before Driving?
There is no fixed number of units that guarantees you will remain below the legal drink driving limit. Although one unit contains approximately 10ml or 8g of pure alcohol in the UK, the amount of alcohol in a drink can vary significantly depending on its strength and size.
For example, a pint of beer, a large glass of wine and a spirit measure can contain very different amounts of alcohol. Even drinks that appear relatively small can affect your ability to drive.
How alcohol affects you also depends on various factors, including your weight, age, sex, metabolism, whether you have eaten recently and how much time has passed since you stopped drinking.
For this reason, calculating how many drinks you can have before driving is only a rough guide. There is no failsafe way to work out your blood alcohol concentration without testing it, and even a single drink could affect your driving.
If you intend to drive, the safest option is not to drink alcohol at all.
What Factors Affect Your Alcohol Level?
Your alcohol level is not determined simply by how much alcohol you drink. Various factors can influence how quickly alcohol enters your bloodstream and how long it remains in your system.
These can include:
- Your body weight and age
- How much alcohol you have consumed
- The strength and size of each drink
- How quickly you have been drinking
- Whether you have eaten recently
- Your individual metabolism
- How much time has passed since drinking
- Whether you are taking medication or other substances
- Your general health and hydration
This means two people who drink the same amount of alcohol can have very different blood alcohol concentrations.
It is therefore impossible to say that three pints, two glasses of wine or a particular number of units will always keep someone below the legal limit.
Does One Drink Put You Over The Drink Drive Limit?
Even one drink can affect your ability to drive, but whether it puts you over the legal alcohol limit depends on the individual and the circumstances.
There is no universal amount of alcohol that corresponds to a particular breath, blood or urine reading. Someone may be under the limit after drinking one alcoholic drink, while another person’s alcohol level could be significantly higher.
It’s also important to remember that being under the legal limit does not necessarily mean you are safe to drive. Alcohol can affect reaction times, concentration, judgement and coordination even when the amount detected is below the legal threshold.
If alcohol has affected your ability to drive, you could potentially face a separate allegation of being unfit to drive through drink, even where a specific alcohol reading is not available.
How Long Does Alcohol Stay In Your System?
A common misconception is that sleeping, drinking coffee, eating a large meal or taking a cold shower will quickly reduce your alcohol level. These measures do not remove alcohol from your bloodstream.
Your body needs time to process the alcohol you have consumed. The rate at which this happens varies from person to person, meaning you cannot reliably predict when you will be below the legal drink drive limit.
This is particularly important the morning after drinking. You may feel completely sober but still have alcohol in your system and potentially be over the legal limit.
If you have been drinking heavily the previous evening, think carefully before driving the following morning.
Can You Refuse A Breath Test?
Refusing to provide a breath, blood, or urine sample without a reasonable excuse is a separate offence under the Road Traffic Act 1988, treated just as seriously as being over the limit itself. Courts rarely accept excuses for refusal unless there’s a genuine medical reason, and a conviction carries the same driving ban and fine as a standard drink driving offence.
What Happens If You’re Over The Legal Limit For Drink Driving?
Being caught over the legal drink driving limit carries serious consequences, and the exact penalty depends on your reading, your driving record, and the circumstances of the stop. Our driving offence solicitors regularly represent clients at every stage of this process, from the first police interview through to sentencing. If you’re facing a charge, get in touch with our team as early as possible.
Penalties For A First Offence
For a first offence of driving or attempting to drive while over the limit, you’ll face an automatic driving ban of at least 12 months, an unlimited fine based on your income, and in the most serious cases, a custodial sentence of up to six months. If you were simply in charge of the vehicle rather than driving it, the penalties are less severe but can still include a fine, penalty points, or a short custodial sentence. Our full guide to drink driving penalties in the UK breaks these down in more detail.
Penalties For Repeat Or High Readings
Where a driver has a previous drink driving law conviction within the last ten years, the minimum ban increases to three years. Very high readings, involvement in a collision, or driving with passengers are all treated as aggravating factors and typically push the sentence above the starting point. High-risk offenders, generally those with a very elevated reading or a repeat conviction, must also pass a medical examination before their licence is reinstated, which can extend a ban well beyond the minimum term.
What To Do If You’ve Been Charged With Being Over The Limit
Don’t assume a guilty plea is your only option, and speak to a solicitor before entering a plea. It’s also worth asking for full disclosure of the calibration and maintenance records for the breath testing device used, since these are sometimes challenged successfully in court.
Keep a note of exactly what happened while it’s fresh in your memory, and get specialist legal advice as early as possible, ideally before your first police interview.
How Our Driving Offence Solicitors Can Help
Knowing where the drink driving limit sits is only the first step. If you’ve been stopped, tested, or charged, the decisions you make in the first few hours can shape the outcome of your case.
Our team has represented clients across London and England from the first police interview through to sentencing, and we know how to challenge weak evidence, disputed readings, and procedural errors.
Get in touch with us today for a confidential consultation.
