Alcohol Unit Calculator

Pick the volume unit. Choose fl oz for US cans and bottles, or mL for anything labelled in metric. The tool converts US fluid ounces at 29.5735 mL each, so 12 fl oz becomes 354.9 mL.

Enter the volume you actually drink. For a can, that is the can size. For a glass, it is what you poured, not what the glass could hold. Enter 12.

Enter the ABV. Look for "ABV" or "alc./vol." on the label and enter 5. Do not enter proof. In the US, proof is twice the ABV, so an 80-proof spirit should be entered as 40.

Read the three results. US standard drinks show 1 (1.00), UK units 1.77, and pure alcohol 14 grams. The mL default of 355 mL gives the same 14.0 g and 1.00 US drink, with 1.775 UK units. The small change comes only from rounding the can size.

To total an evening, run each drink separately and add the results. The tool handles one drink at a time.

Pure alcohol (g) = V × (ABV ÷ 100) × 0.789, where V is the volume in millilitres and 0.789 g/mL is the density of ethanol at room temperature. The first part, V × ABV ÷ 100, is the volume of pure alcohol. Multiplying by density turns it into a mass.

US standard drinks = grams ÷ 14. The National Institute on Alcohol Abuse and Alcoholism defines one US standard drink as about 14 grams of pure alcohol, or 0.6 fl oz.

UK units = V × ABV ÷ 1,000. The NHS defines one unit as 10 mL of pure alcohol. The formula counts millilitres of alcohol and divides by 10, so it never uses density. Ten millilitres weighs about 7.9 g, which is why the NHS describes a unit as roughly 8 grams.

Why every 1.00 US drink shows 1.77 UK units. A US drink is 14 g, and a UK unit is 7.89 g. The ratio is fixed at about 1.77, whatever the drink. If one figure looks wrong, check the other: they should always keep that proportion.

Enter 750 mL and 13.5%. The bottle contains 750 × 0.135 = 101.25 mL of pure alcohol, which is 79.9 g. That is 5.71 US standard drinks and about 10.1 UK units (750 × 13.5 ÷ 1,000 = 10.125).

The common idea that a bottle is five glasses assumes two things: a 5 fl oz pour and 12% wine. A 750 mL bottle at 12% comes to 5.07 US drinks and 9.00 UK units, close to that idea. Most red wines are stronger. At 13.5%, a 5 fl oz pour is 1.13 US drinks, not 1.00, so the same bottle holds almost six standard drinks.

In UK terms, one bottle of 13.5% wine is 10.1 units. The UK Chief Medical Officers' low-risk drinking guidelines (2016) advise no more than 14 units a week, spread over three or more days. One bottle is therefore close to three-quarters of that weekly amount. The calculator reports units only and does not score your total against any guideline.

Home wine pours. A generous 8 fl oz glass of 13.5% wine is 1.80 US drinks. Even a 6 fl oz pour is 1.35. Large wine glasses make a standard 5 oz pour look small, so people pour more.

Pints and strong beer. A 16 fl oz pint of 5% beer is 1.33 US drinks, and a 16 fl oz pint of 7% IPA is 1.87. A 12 fl oz can of 9% beer is 1.80. A 40 fl oz bottle of 8% malt liquor is 5.33 US drinks.

Free-poured spirits. A 2 fl oz pour of 40% spirit is 1.33 US drinks and a 3 fl oz pour is 2.00. Cocktails often contain more than one spirit, so enter each one separately.

UK glass sizes. A 250 mL large glass of 13% wine is 3.25 units, while a 125 mL small glass of 12% wine is 1.50. On a menu both are just "a glass of wine".

Going the other way. A 12 fl oz light beer at 4.2% is 0.84 US drinks. Lower-strength drinks count for less, but only if the volume stays the same.

To find out what you really pour, fill your usual glass to your usual level with water, measure it once, and enter that volume.

Grams of alcohol tell you how much you drank. They do not tell you how much is in your blood, or how impaired you are. Blood alcohol concentration depends on body weight, sex, food in the stomach, how quickly you drank, and how much time has passed. Two people who drink the same 1.00 standard drink can end up with quite different levels.

The BAC calculator takes those factors and gives an estimate, but no calculator can confirm that you are safe to drive. Impairment begins before legal limits are reached. The only reliable choice is not to drive after drinking. People who are pregnant, taking medicines that interact with alcohol, or under the legal drinking age should not use unit counts as permission to drink.

The results are only as accurate as the label and the volume you enter. Labelled ABV is allowed to differ slightly from the true strength, and poured volumes are usually estimates. The tool reports the US and UK definitions only, and other countries use other sizes, such as 10 grams in Australia. It handles one drink at a time, and it does not estimate blood alcohol, impairment, calories, or health risk. It is an educational conversion tool, not medical advice.

For how those grams might translate into a blood alcohol level over an evening, the BAC calculator is the tool to use. Remember that it is an estimate, not a green light to drive. Alcohol also provides about 7 kcal per gram, so the 14 g in one standard drink adds roughly 98 kcal before any sugar or mixer. The calorie calculator and the TDEE calculator show how that fits into your daily energy needs.