One unit of alcohol equals 10 milliliters (8 grams) of pure ethanol. That’s the UK measurement. If you’re in the United States, the equivalent concept is a “standard drink,” which is larger: 14 grams of pure ethanol. These two systems measure the same thing but use different amounts, which matters when you’re reading health guidelines or tracking your intake.
UK Units vs. US Standard Drinks
The UK and US use different baselines, and mixing them up can lead to real miscalculations about how much you’re drinking.
A UK unit contains 8 grams of pure alcohol. A US standard drink contains 14 grams. That means one US standard drink equals roughly 1.75 UK units. If you see a health guideline referencing “units,” check whether it’s using the UK or US definition before applying it to your own habits.
What One Unit Looks Like in Your Glass
Using the UK system (8 grams per unit), one unit is smaller than most people expect. It’s roughly a third of a pint of regular-strength beer (about 170 ml at 5% ABV), or a small 76 ml glass of wine at 12% ABV, or a single 25 ml measure of spirits at 40% ABV. A standard pub pour of wine (175 ml) is actually about 2.1 units, not one.
In the US system (14 grams per standard drink), one drink lines up more closely with typical serving sizes:
- Regular beer: 12 fluid ounces (a standard can) at 5% ABV
- Wine: 5 fluid ounces at 12% ABV
- Spirits: 1.5 fluid ounces (a single shot) at 40% ABV
- Malt liquor or hard seltzer: 8 to 10 fluid ounces at about 7% ABV
- Fortified wine (sherry, port): 3 to 4 fluid ounces at about 17% ABV
- Liqueurs: 2 to 3 fluid ounces at about 24% ABV
The key insight: stronger drinks come in smaller volumes to equal the same amount of alcohol. A 12-ounce beer and a 1.5-ounce shot contain the same amount of pure ethanol.
How to Calculate Units Yourself
You can figure out how many UK units are in any drink using a simple formula: multiply the volume of the drink in milliliters by its ABV percentage, then divide by 1,000. So a 750 ml bottle of wine at 13% ABV contains 9.75 units (750 × 13 ÷ 1,000). A 330 ml bottle of 5% beer contains 1.65 units.
For US standard drinks, the math is similar but the reference amount is different. Multiply the volume in ounces by the ABV percentage, then divide by 0.6. Or just remember that 0.6 fluid ounces of pure alcohol equals one standard drink.
Most bottles and cans sold in the UK now list the unit count on the label. In the US, standard drink equivalents are less commonly printed, but the ABV is always there, so you can work it out.
How Fast Your Body Processes One Unit
The average adult liver breaks down alcohol at a fairly fixed pace: roughly one UK unit per hour, or about one US standard drink per hour. Nothing speeds this up. Coffee, food, water, and cold showers don’t change the rate. Time is the only factor that clears alcohol from your system.
That said, “average” is doing a lot of work in that sentence. Your actual processing speed depends on body size and weight, the ratio of muscle to fat in your body, hormone levels, and biological sex. Women generally absorb more alcohol and take longer to process it than men, even when drinking the same amount. This is partly because men tend to have more body water (which dilutes alcohol) and more of the enzymes that break it down. Medications and overall liver health also play a role.
Weekly Limits in Current Guidelines
The UK Chief Medical Officers’ guideline recommends no more than 14 units per week for both men and women. That’s the equivalent of about 6 pints of average-strength beer or roughly 6 medium glasses of wine spread across the week. The guidance also stresses spreading those 14 units over three or more days rather than concentrating them into one or two sessions, because binge patterns increase the risk of both long-term illness and acute injuries.
In the US, federal dietary guidelines define moderate drinking as up to 2 standard drinks per day for men and up to 1 for women. Because a US standard drink is nearly double a UK unit, these guidelines land in a broadly similar range when converted: 14 US standard drinks per week for men works out to about 24.5 UK units, which is actually higher than the UK threshold. The UK guidelines are among the more conservative in the world.
Whatever system you use, the practical takeaway is the same. Most people underestimate how much they drink because real-world pours are bigger than the official definitions. A large glass of wine at a restaurant is often 250 ml, which is 3 UK units or roughly 1.7 US standard drinks. Pouring spirits at home without a measure easily doubles the “standard” amount. Counting accurately starts with knowing what one unit actually looks like in a glass, and for most people, it’s smaller than they expect.