BAC Calculator — UK Drink-Drive Limits 2026
Estimate your blood alcohol content (BAC) based on what you drank, your body weight, and time elapsed. See how your estimated BAC compares to UK drink-drive limits — 0.08% for England, Wales, and Northern Ireland, or 0.05% for Scotland — and find out when you might be clear.
Reviewed by Richard Ross · Last updated April 2026
How BAC Calculator — UK Drink-Drive Limits 2026 works
The Widmark formula
The Widmark formula estimates blood alcohol content from the mass of alcohol consumed, body weight, and a sex-specific body water constant (0.68 for males, 0.55 for females). These constants reflect differences in body composition — men have proportionally more water-containing tissue. The formula is: BAC = (alcohol grams / (weight kg x 1000 x body water constant)) x 100. Alcohol metabolism then reduces BAC at approximately 0.015% per hour.
UK drink-drive limits
In England, Wales, and Northern Ireland, the legal limit is 80 mg of alcohol per 100 ml of blood (0.08%). Scotland has a lower limit of 50 mg per 100 ml (0.05%), aligned with most of Europe. These are legal thresholds, not safety thresholds — cognitive impairment begins at lower levels. The maximum safe BAC for driving is zero.
The morning after
Alcohol consumed the night before can still put you over the limit the following morning. A heavy night's drinking (8+ units) can take 12 or more hours to clear fully. If you were drinking late, use our morning-after calculator to estimate whether your BAC may still be above the legal limit before driving. This is one of the most common causes of drink-drive offences — people assume they are fine the next day when they are not.
Standard UK drinks and units
One UK unit is 10 ml (8g) of pure alcohol. A pint of 4% beer contains about 2.3 units. A 175 ml glass of 13% wine contains about 2.3 units. A large (250 ml) glass of wine is about 3.3 units. A single 25 ml measure of 40% spirit is 1 unit; a double is 2 units. The NHS recommends no more than 14 units per week, spread over 3 or more days, with several alcohol-free days each week.
How UK drink-drive limits compare internationally
The UK (England, Wales, NI) limit of 0.08% is among the highest in Europe. Scotland lowered its limit to 0.05% in 2014, aligning with most EU countries including France, Germany, Spain, and Italy. Several countries — including Sweden, Norway, Poland, and Russia — set even lower limits at 0.02%. The USA has a federal limit of 0.08%, the same as England. Australia and Canada use 0.05% nationally. Many road safety groups have called for England, Wales, and NI to follow Scotland's example.
Penalties for drink-driving in the UK
Drink-driving in the UK carries severe penalties. Being in charge of a vehicle while above the legal limit can result in 3 months' imprisonment, a fine of up to £2,500, and a possible driving ban. Driving or attempting to drive while above the limit carries up to 6 months' imprisonment, an unlimited fine, and a minimum 12-month driving ban. Causing death by careless driving when under the influence carries up to 14 years' imprisonment, an unlimited fine, a minimum 2-year driving ban, and an extended retest requirement. A drink-drive conviction stays on your licence for 11 years and can significantly increase insurance costs.
Why this is only an estimate
Actual BAC depends on many factors this calculator cannot account for: food consumption (eating slows alcohol absorption significantly), liver health, medications, genetic variation in alcohol metabolism enzymes, body fat distribution, and whether you are hydrated. Individual metabolism rates vary by a factor of three or more between people. These estimates should never be used to make decisions about driving or other safety-critical activities.
How to get alcohol out of your system
The only reliable way to reduce BAC is time. Coffee, food, water, exercise, and sleep do not speed metabolism of alcohol already in the bloodstream — they may make you feel more alert but do not lower BAC. If you have been drinking, the only safe approach is to wait the necessary hours before driving or operating machinery.
Frequently asked questions
What is the UK drink-drive limit?
80 mg of alcohol per 100 ml of blood (0.08% BAC) in England, Wales, and Northern Ireland. Scotland has a lower limit of 50 mg per 100 ml (0.05% BAC). These are legal limits — driving with any alcohol in your system increases risk. Many road safety organisations recommend not drinking at all if you intend to drive.
Can I still be over the limit the morning after drinking?
Yes — this is one of the most common causes of drink-drive offences. Alcohol is metabolised at roughly 0.015% BAC per hour. A heavy night's drinking (8+ units) can easily take 12 or more hours to clear completely. If you were drinking until midnight, you could still be over the limit at 8am the next morning. Use our morning-after calculator for a personalised estimate.
How long does alcohol stay in your system?
Your body metabolises alcohol at roughly 0.015% BAC per hour on average, but this varies significantly between people. A pint of beer (approximately 2-3 units) might take 2-3 hours to clear. After a heavy night's drinking, alcohol can remain in your system until the following afternoon.
Can I use this calculator to decide whether to drive?
No. This calculator is for educational purposes only. Individual metabolism varies enormously. You could have a lower BAC than predicted and still be impaired. Or your BAC could be higher. The only safe policy is to not drive after drinking any alcohol.
What is a standard unit of alcohol?
One UK unit is 10 ml (8g) of pure alcohol. A pint of 4% beer contains about 2.3 units; a 175 ml glass of 13% wine contains about 2.3 units; a 25 ml single measure of 40% spirit contains 1 unit; a double spirit (50 ml) is 2 units. The NHS recommends not regularly drinking more than 14 units per week.
What are the penalties for drink-driving in the UK?
Driving or attempting to drive while above the legal limit carries up to 6 months' imprisonment, an unlimited fine, and a minimum 12-month driving ban. Causing death by careless driving under the influence can result in up to 14 years' imprisonment. A conviction stays on your licence for 11 years.
Why does Scotland have a lower limit?
Scotland lowered its drink-drive limit from 0.08% to 0.05% in December 2014 to align with most European countries. Evidence shows that impairment begins well below 0.08%, and countries with lower limits tend to have fewer alcohol-related road deaths. There have been ongoing calls for England, Wales, and Northern Ireland to follow suit.
How many drinks can I have and still drive?
There is no safe number of drinks that guarantees you will be under the limit. BAC depends on your weight, sex, metabolism, food intake, and many other factors. Two people drinking the same amount can have very different BAC levels. The only safe answer is: if you plan to drive, do not drink at all.
Does eating food reduce your BAC?
Eating food before or while drinking slows the absorption of alcohol into the bloodstream, which lowers the peak BAC you reach. However, it does not reduce the total amount of alcohol that enters your system — it just delays it. Once alcohol is in your bloodstream, food does not speed its removal. Only time reduces BAC.
What BAC level causes alcohol poisoning?
Alcohol poisoning typically occurs at BAC levels above 0.30% (300 mg per 100 ml of blood), but serious symptoms can begin at lower levels. At 0.20%, most people experience significant impairment, confusion, and risk of vomiting. Above 0.35%, there is a risk of coma and death. If someone is unconscious, breathing slowly, or has cold/blue skin after drinking, call 999 immediately.
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This is a rough estimate only. Never use this to decide whether to drive. Do not drive if you have been drinking. This calculator provides estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.