Standard Drink Calculator – Alcohol Units & BAC
Calculate standard drinks, alcohol units, estimated blood alcohol concentration, and calories from any alcoholic beverage.
Enter your drink details and personal data to see how many standard drinks you have consumed, your estimated BAC, and caloric impact.
Standard Drink Calculator – Alcohol Units & BAC
Calculate standard drinks, alcohol units, estimated blood alcohol concentration, and calories from any alcoholic beverage.
About the Standard Drink Calculator
Understanding how much alcohol you are consuming requires more than just counting glasses — it requires converting different beverages into standardized units of pure alcohol. This calculator does exactly that, transforming any combination of volume and alcohol by volume (ABV) percentage into standard drinks, UK alcohol units, estimated blood alcohol concentration (BAC), and calories, giving you a complete picture of your alcohol intake in a single step.
A standard drink in the United States contains exactly 14 grams of pure alcohol, regardless of the beverage type. This standardization means that a 12-ounce (355 mL) beer at 5% ABV, a 5-ounce (148 mL) glass of wine at 12% ABV, and 1.5 ounces (44 mL) of distilled spirits at 40% ABV each contain approximately 14 grams of pure alcohol and each count as one standard drink. In the United Kingdom, the unit system differs slightly: one UK unit contains 10 mL (about 8 grams) of pure alcohol. This calculator reports both measures so you can use whichever standard applies in your country or context.
The pure alcohol content of any drink is calculated by multiplying the volume in milliliters by the ABV fraction and by the density of ethanol (0.789 g/mL). For example, a 500 mL beer at 5% ABV contains 500 × 0.05 × 0.789 = 19.7 grams of pure alcohol — approximately 1.4 US standard drinks or 2.5 UK units. Recognizing that a large pub beer exceeds one standard drink is a key insight for anyone trying to track their consumption accurately against health guidelines.
Blood alcohol concentration (BAC) is calculated using the Widmark formula, the most widely used pharmacokinetic model for alcohol metabolism. The formula accounts for the amount of alcohol consumed, body weight, sex-based differences in body water distribution (the Widmark r factor is approximately 0.68 for men and 0.55 for women, reflecting the higher proportion of body fat and lower total body water in women), and the time elapsed since drinking. Alcohol is eliminated at a roughly constant rate of 0.015% BAC per hour in most adults, although this varies with food intake, liver health, and genetic factors. The BAC estimate is approximate and should never be used to justify driving.
Calories from alcohol are calculated at approximately 7 kilocalories per gram of pure ethanol — more energy-dense than carbohydrates or protein (both 4 kcal/g) but less than fat (9 kcal/g). Alcoholic beverages also typically contain carbohydrates and sugars that add additional calories beyond the alcohol itself; this calculator reports only the calories derived from the ethanol content. Regular drinkers often underestimate how significantly alcohol contributes to daily caloric intake: a daily large glass of wine can add over 200 calories, contributing to weight gain over time.
Health guidelines vary by country, but most recommend no more than 14 UK units (about 10 US standard drinks) per week, spread over at least three days, with some alcohol-free days each week. Binge drinking — defined as consuming enough alcohol to raise BAC above 0.08% in a single session — carries acute risks including impaired judgment, accidents, and alcohol poisoning, as well as long-term health consequences with regular repetition. This calculator is for harm-reduction awareness and does not constitute medical advice.
Standard drink examples
These examples illustrate how different drinks and personal factors affect standard drink counts and estimated BAC.
| Drink & person | Standard drinks / BAC | Health context |
|---|---|---|
| 330 mL beer 5%, 70 kg male, 1.5 h | 1.2 drinks / ~0.01% BAC | One standard can of beer, well below any legal driving limit after 1.5 hours. |
| 175 mL wine 12%, 65 kg female, 2 h | 1.5 drinks / ~0.02% BAC | A standard wine glass for a woman; about 1.5 standard drinks, mildly above zero BAC. |
| 500 mL beer 5%, 80 kg male, 0.5 h | 1.4 drinks / ~0.04% BAC | A pint of regular beer shortly after consumption; noticeable impairment begins. |
| 200 mL cocktail 15%, 60 kg female, 0.25 h | 1.7 drinks / ~0.07% BAC | A strong cocktail for a smaller woman soon after drinking; BAC is near or above safe driving limits. |
How to use the Standard Drink Calculator
- Measure or estimate the volume of your drink in milliliters and check the alcohol percentage (ABV) on the label or menu.
- Select the drink type (Beer, Wine, Spirit, Cocktail, or Other) for reference context, then enter your body weight in kg and your biological sex.
- Enter the time since you started drinking in hours; for a drink you just finished, enter 0 or a small value like 0.25.
- Click 'Calculate' to see pure alcohol content (grams), standard drinks (US), alcohol units (UK), estimated BAC, and calories.
- If BAC is above 0.05%, avoid driving; above 0.08% is illegal for driving in most jurisdictions. Use the Reset button to evaluate another drink or scenario.
Standard drink calculator FAQ
What is a standard drink?
A standard drink contains a fixed amount of pure alcohol regardless of the beverage type. In the United States, one standard drink contains 14 grams (0.6 fluid ounces) of pure alcohol. In the UK, one unit contains 10 mL (8 grams) of pure alcohol. Different countries use different standards, which is why this calculator reports both US and UK measures.
How is BAC calculated?
This calculator uses the Widmark formula: BAC = (pure alcohol in grams × 0.1) / (body weight in kg × r) − (0.015 × hours elapsed), where r is the Widmark distribution factor (0.68 for males, 0.55 for females). The result is an estimate; real BAC is affected by food intake, medication, liver health, and individual metabolism. Never use a BAC estimate to decide whether to drive.
Why do women typically have a higher BAC than men for the same drink?
Women generally have a higher percentage of body fat and lower total body water than men of the same weight, which means alcohol is distributed into a smaller volume of water and becomes more concentrated. Women also tend to have lower levels of the enzyme alcohol dehydrogenase in the stomach, so more alcohol enters the bloodstream unchanged. As a result, the same drink produces a higher BAC in a woman compared with a man of the same body weight.
How many calories are in alcohol?
Ethanol contains approximately 7 kilocalories per gram, making it more calorie-dense than carbohydrates or protein (both 4 kcal/g). This calculator reports only the calories from pure ethanol; most drinks also contain carbohydrates and sugars that add additional calories. For example, a 330 mL beer at 5% ABV provides about 97 kcal from alcohol alone plus additional calories from sugars.
What are safe drinking guidelines?
Most health authorities recommend no more than 14 UK units (approximately 10 US standard drinks) per week for both men and women, with at least two alcohol-free days per week and no binge drinking. Many guidelines now state that no amount of alcohol is completely risk-free for health. Pregnant women, individuals on certain medications, and people with liver disease should avoid alcohol entirely.