What's in a drink?

In the real world, alcoholic drinks come in all kinds of shapes, sizes and strengths. So how can we know how strong each drink is?

Once upon a time . . .

It used to be a lot easier to work out how much drink you were getting. A pint of beer used to equal two units, a shot of spirits one unit. Nowadays, beers, lagers and wines are all generally stronger and spirits are commonly sold in measures that are over a unit and . . .

Stop right there! Can someone please tell me what a 'Unit' is?
A UK 'unit' is 10ml of pure alcohol.

Why this amount?

It's all to do with how our bodies deal with alcohol. On average, healthy adult bodies can break down 10ml of alcohol in an hour. So, if you drink 10ml of alcohol, 60 minutes later there shouldn't be any left in your bloodstream.

Where does the alcohol go?

The liver breaks down most of it, though a small amount escapes through the skin, on the breath and in our urine.

So what does 'ABV' mean?

ABV stands for Alcohol By Volume. All pre-packaged alcoholic drinks must state how strong they are. Strength is shown as a percentage, with the letters ABV after the number. For example, most popular wines today are around 13% ABV, beers around 3.8% ABV.

Advice on 'sensible drinking' uses units – how do they work?

To find out how many units are in a drink, you need to know

its volume in millilitres
its %ABV strength

Most packaged drinks state their volume in millilitres (ml). However, bottles of spirits and wine often state their volume in centilitres (cl). To get from centilitres to millilitres, simply stick another zero on the end. So, 75cl = 750ml.

To find out how many units of alcohol are in a drink:

Multiply the volume (in millilitres) by %ABV then divide the result by 1000.

Units = (volume (ml) x %ABV)
1000

What about the strengths and measures in your Session Calculator?

To keep you out of trouble, we've been generous! We realise that some wines are only 9% ABV but the most popular ones average around 13%. We also know that many bars and clubs now sell spirits in 35ml singles and 70ml doubles rather than the more traditional 25ml and 50ml measures. That's why we've included a range of drink sizes in our calculator.

How accurate is the Session Calculator?

The session calculator is intended only as a rough guide to how much you're drinking, If you want to know exactly, you need to measure the volume of every drink you take precisely and find out what its %ABV is (there can be large differences between brands).

NEVER USE THE SESSION CALCULATOR TO WORK OUT IF YOU'RE SAFE TO DRIVE

Safe limits for driving are based on how much alcohol is in your blood, not how much you've drunk. All kinds of things affect how alcohol is absorbed so don't even bother trying to work it out – you can't.

For that, you need a breathalyser. Better still - if you're drinking, give the car keys to someone else who isn't.

Next page: Health facts and figures