Skip to content 
Alcohol Unit Calculator
Instantly calculate the units in any drink, track your weekly intake against health guidelines, and understand your personal risk level — all in one place.
Units = (Volume ml × ABV%) ÷ 1000 | BAC Level | Effect | Legal to Drive? |
|---|---|---|
| < 0.02% | Minimal effect | ✓ UK/US Legal |
| 0.02–0.05% | Relaxation, mild impairment | ✓ UK Legal (0.08 limit) |
| 0.05–0.08% | Coordination impaired | ⚠ Scotland illegal |
| 0.08–0.15% | Clear impairment, slurred speech | ✗ Illegal everywhere |
| > 0.15% | Severe impairment, danger | ✗ Dangerous |
| Drink | Volume | ABV | UK Units | Calories | Risk Level |
|---|---|---|---|---|---|
| Pint Lager (4%) | 568 ml | 4% | 2.3 | ~182 | Low |
| Pint Lager (5.2%) | 568 ml | 5.2% | 3.0 | ~218 | Moderate |
| Wine (medium, 13%) | 175 ml | 13% | 2.3 | ~159 | Low |
| Wine (large, 13%) | 250 ml | 13% | 3.3 | ~228 | Moderate |
| Single Spirit (40%) | 25 ml | 40% | 1.0 | ~56 | Low |
| Double Spirit (40%) | 50 ml | 40% | 2.0 | ~112 | Low |
| Alcopop (5%) | 275 ml | 5% | 1.4 | ~186 | Low |
| Prosecco Flute (12%) | 125 ml | 12% | 1.5 | ~95 | Low |
| Strong Cider (7.5%) | 500 ml | 7.5% | 3.8 | ~226 | High |
What Is an Alcohol Unit?
An alcohol unit is a standardised measure of pure alcohol content in a drink. In the United Kingdom, one unit equals exactly 10 ml (or 8 grams) of pure ethanol. This system was introduced to give people a practical, consistent way to track their drinking without needing a chemistry degree — because raw percentages printed on labels mean very little unless you also know the volume you’re drinking.
The unit system is primarily a UK and European measure. In the United States, a “standard drink” contains 14 grams of pure alcohol; in Canada, it’s 13.6 grams; in Australia, 10 grams (the same as the UK). The differences seem small but add up over a week — which is why our calculator lets you toggle between all four systems.
Understanding units matters because health guidelines, liver health research, and NHS guidance are all published in units. Without being able to convert your actual drinking habits into units, official recommendations are essentially meaningless to you.
The Alcohol Unit Formula Explained
The calculation is straightforward once you know what you’re looking for. To work out UK alcohol units in any drink:
For example, a standard pint (568 ml) of 4% lager: (568 × 4) ÷ 1000 = 2.27 units. A large 250 ml glass of 13% wine: (250 × 13) ÷ 1000 = 3.25 units. A double measure (50 ml) of 40% spirits: (50 × 40) ÷ 1000 = 2.0 units exactly.
For US standard drinks, the formula adjusts to account for the density of ethanol (0.789 g/ml): Standard Drinks = (Volume ml × ABV% × 0.789) ÷ 14. The density factor ensures your result is in grams rather than millilitres of pure alcohol.
UK Chief Medical Officers’ Drinking Guidelines
The UK Chief Medical Officers published updated low-risk drinking guidelines in 2016, and they remain the official benchmark today. The guidance applies equally to men and women — a change from older guidelines that gave men a higher allowance.
Weekly Limit
No more than 14 units per week for both men and women to keep health risks low.
Spread It Out
Drink across 3 or more days if you regularly consume up to 14 units. Bingeing the same 14 units in one night is far more harmful.
Drink-Free Days
Build in several alcohol-free days each week to break habitual drinking and give your liver recovery time.
Pregnancy
The safest approach when pregnant or trying to conceive is no alcohol at all. There is no established safe level.
What Does 14 Units Actually Look Like?
Fourteen units is roughly 6 pints of 4% beer, or 6 medium (175 ml) glasses of 13% wine, or 14 single measures of 40% spirits. Written that way, it may sound like quite a lot — but many people drink that amount over a single weekend without realising it. A Saturday night that includes 4 pints and a couple of large wines is already flirting with 14 units on its own.
How Alcohol Affects the Body Over Time
Ethanol is processed primarily by the liver, which can metabolise approximately one UK unit per hour in most adults. This rate is relatively consistent regardless of what you drink, how much water you consume, or whether you eat — common myths like “beer before wine” have no scientific basis whatsoever. The liver simply works at its own pace.
Short-term effects begin almost immediately. Even at a blood alcohol concentration (BAC) of 0.02–0.03%, reaction times slow measurably. At 0.05%, coordination is impaired enough to affect driving ability — which is why Scotland lowered its drink-drive limit to 50 mg/100 ml (0.05%) in 2014. By 0.08%, the legal limit in England, Wales, and the US, most people show clear signs of impairment.
Long-term, the risks compound. Regular consumption above 14 units per week is linked to an elevated risk of liver disease, certain cancers (particularly breast and bowel), cardiovascular disease, high blood pressure, and cognitive decline. The UK NHS estimates that roughly 1 in 5 adults drink at hazardous or harmful levels without being dependent — meaning the harm is accumulating without the warning signs of addiction.
Alcohol Units vs Standard Drinks: Regional Differences
One of the most confusing aspects of alcohol health messaging is that different countries use completely different measures. A “standard drink” in the US is 40% larger than a UK unit. This means that if you’re reading American guidelines and applying them in a UK context, you’re almost certainly underestimating your intake.
| Country | Measure Name | Pure Alcohol | Weekly Guideline (Men) | Weekly Guideline (Women) |
|---|---|---|---|---|
| 🇬🇧 United Kingdom | Unit | 8 g / 10 ml | 14 units | 14 units |
| 🇺🇸 United States | Standard Drink | 14 g | ≤ 14 drinks/week | ≤ 7 drinks/week |
| 🇨🇦 Canada | Standard Drink | 13.6 g | ≤ 15 drinks/week | ≤ 10 drinks/week |
| 🇦🇺 Australia | Standard Drink | 10 g | ≤ 10 drinks/week | ≤ 10 drinks/week |
The takeaway: always check which standard your source is using. Our calculator handles all four automatically when you select your region.
Blood Alcohol Concentration (BAC): How It’s Calculated
BAC measures the concentration of ethanol in your bloodstream, expressed as a percentage. The most widely used estimation method is the Widmark formula, developed by Swedish pharmacologist Erik Widmark in the 1920s and still used in forensic toxicology today.
The simplified Widmark formula: BAC = (Alcohol consumed in grams) ÷ (Body weight in grams × Distribution factor) − (Metabolism rate × Hours elapsed). The distribution factor is typically 0.68 for males and 0.55 for females, reflecting the difference in average body water content. The metabolism rate is approximately 0.015% per hour.
This explains why two people can drink identical amounts and have noticeably different BAC levels: body weight, body composition, and whether they’ve eaten all play a significant role. Food slows alcohol absorption by keeping it in the stomach longer, which is why drinking on an empty stomach raises BAC more rapidly.
Alcohol and Calories: The Hidden Numbers
Alcohol is the second most calorie-dense macronutrient after fat, providing 7 calories per gram of ethanol. This is almost double the energy density of protein or carbohydrates. Unlike the calories from protein or complex carbs, alcohol calories have no nutritional value — they don’t build muscle, stabilise blood sugar, or support cellular function. They are pure energy with no payback.
In practical terms: a large glass of wine (250 ml, 13%) contains around 228 calories. Three large glasses is equivalent to a full extra meal. A pint of 5% lager runs to roughly 215 calories. For anyone managing their weight, tracking alcohol alongside food intake is essential — and yet most calorie-counting apps and diet plans systematically undercount it.
Our multi-drink calculator estimates session calories automatically, using the industry-standard formula: Calories ≈ (Volume ml × ABV% × 0.789 × 7) ÷ 100, with a small addition for fermentation by-products in beer and wine.
Binge Drinking: Definition and Risks
The NHS defines binge drinking as consuming more than 6 units in a single session for women, and more than 8 units for men. That’s roughly equivalent to two large glasses of wine, or two to three pints of standard lager — amounts many people would not classify as a “binge” in everyday conversation.
The health risks of binge drinking differ from those of chronic heavy drinking. Acutely, even a single binge can cause alcohol poisoning, dangerous cardiac arrhythmias, accidents and injuries, and acute liver stress. Over time, repeated bingeing is associated with increased risk of stroke, brain damage, and the same cancers linked to chronic drinking — even if your overall weekly intake stays nominally within guidelines.
The key insight from researchers is that how you drink matters as much as how much. Consuming 14 units across six days is meaningfully safer than consuming them in a single Saturday night session, because peak BAC, acute liver stress, and impairment risk are all determined by the rate of consumption, not the weekly total.
Using This Calculator: Step-by-Step Guide
Single Drink Tab
Select a common drink from the quick-pick grid or enter any custom volume and ABV. Instantly see units, percentage of weekly guideline, and risk level.
Multi-Drink Session
Build your full night out drink by drink. Get total units, calories, and an overall risk assessment for the whole session.
Weekly Tracker
Log units day by day across the whole week. Live totals, drink-free day counts, and progress against the 14-unit guideline update as you type.
BAC Estimate
Enter your weight, sex, units consumed, and hours drinking. Get an estimated blood alcohol concentration and approximate time until sober.
How to Cut Down: Evidence-Based Strategies
If you’ve used the tracker and found your weekly total higher than expected, the good news is that even modest reductions in alcohol intake produce measurable health benefits within weeks. Research shows liver function improves within days of abstinence, sleep quality typically improves within two weeks, and cardiovascular markers begin to normalise within a month.
- Swap to lower-strength options. Replacing a 5.2% pint with a 3.6% session ale saves almost one full unit per pint. Across a week, that adds up to several units without changing how much you drink.
- Use smaller measures. A small wine glass (125 ml) contains 1.5 units vs. 3.25 units for a large glass — less than half the units for a comparable social experience.
- Alternate with soft drinks. Drinking a glass of water or a soft drink between alcoholic drinks halves your unit intake and dramatically slows down your BAC rise.
- Plan drink-free days in advance. Research on habit formation shows that pre-committing to specific days is far more effective than trying to be spontaneously moderate.
- Don’t “save up” your units. Consuming 14 units in one night is not the same as consuming 2 units a day, even though the arithmetic is identical. Spread your drinking over as many days as possible.
- Track before you drink, not after. Use this calculator at the start of a session to set a conscious target, rather than retrospectively assessing damage done.
Frequently Asked Questions
A standard 750 ml bottle of wine at 13% ABV contains (750 × 13) ÷ 1000 = 9.75 units — nearly 10 units. At 14%, a bottle contains 10.5 units. This means a single bottle of wine exceeds two-thirds of the entire weekly low-risk guideline for one person.
The liver processes roughly one UK unit per hour. A person who has consumed 8 units (e.g. 4 pints of 4% lager) needs approximately 8 hours to clear their system — meaning alcohol consumed at midnight may still be detectable the following morning. BAC can remain above the driving limit the morning after a heavy night even if you feel perfectly sober.
Under current UK CMO guidelines (updated 2016), both men and women are advised to stay below 14 units per week. This is a change from previous guidance, which allowed men 21 units. The revision reflects updated evidence on cancer risk, which applies equally to both sexes. However, women typically achieve higher BAC from the same amount of alcohol due to lower body water content and different enzyme levels.
“Increasing risk” drinking is 14–35 units per week for women and 14–50 units per week for men. “High risk” (sometimes called harmful) drinking is above 35 units per week for women and 50 units per week for men. These categories are used by NHS clinicians and the AUDIT screening tool to assess whether someone would benefit from intervention.
Alcohol-free beers (under 0.5% ABV) contain negligible units — a 330 ml can at 0.5% is just 0.17 units. Low-alcohol beers (typically 0.5–1.2% ABV) are similarly low. You can enter any ABV value into our calculator to check; the formula works the same way at all alcohol strengths.
No. Coffee makes you feel more alert but does not accelerate liver metabolism of alcohol. Food slows the absorption of alcohol into the bloodstream (reducing peak BAC) but has no effect on how quickly your body processes alcohol already in circulation. The only reliable way to lower BAC is time.
The unit calculation (Volume × ABV ÷ 1000) is mathematically precise based on the values you enter. The BAC estimate is an approximation based on the Widmark formula and carries inherent uncertainty due to individual variation in metabolism, body composition, food intake, and tolerance. It should be treated as a guide rather than a definitive reading.
Resources and Further Reading
For authoritative guidance on alcohol and health, the following sources are recommended: the NHS Alcohol Advice pages, Drinkaware’s unit guides, the UK Chief Medical Officers’ Low Risk Drinking Guidelines (2016), and the World Health Organization’s Global Status Report on Alcohol and Health. Our calculator implements the same unit definitions used by these official bodies.
