It was so much easier in the old days. A small glass of wine. Half a pint of lager. Or a small whisky. That is what I have been told anyway (I am just 23 years old). It would seem in the last decade wine glasses have enlarged, lager has become more potent and spirit measures more varied, and the system for counting has become more complex. 

"In the old days" drinks all contained roughly one unit of alcohol apparently, which is 10ml of pure alcohol. At least, that was the general rule of thumb, and what I have been told in some of the focus groups I run. Today we have become a little bleary eyed when it comes to units. Do we really know? 

It seems not. This week the ONS released their latest figures on alcohol consumption in the UK and a whopping 2.5 million people in Great Britain - 9% of drinkers - consume more than the new weekly recommended limit for alcohol in a single day.

I have come to know through my work that a single 25ml measure of a 40% spirit is one unit, but I have to admit I am just as confused as the people in my focus groups when it comes to understanding units. What happens to units when you drink different strengths of alcohol? What about cocktails? How can I tell if this wine glass is a large or medium and just how many units are in that long island iced tea exactly? Ask me how many glasses I had and I can tell you. But ask me how many units and I will guess. 

And that is the point. We are a nation of estimators when it comes to units and drinks and we are grossly underestimating. What people think they drink and what they actually drink - make up a huge national deficit. The difference between consumption figures supplied by the General Household Survey and figures from alcohol sales is 430 million units a week, or a bottle of wine per adult drinker per week. 

Another reason why people underestimate their intake is that they tend to pour large measures when drinking at home. Our research into home drinking two years ago found that many people poured double or triple measures thinking it was one 25ml measure. This means that many people are unintentionally exceeding the daily unit guidelines and inadvertently putting themselves at risk of the physical, social and mental harms associated with drinking to excess.

I am interested in understanding what units really mean to people. So far my conclusion has been 'very little'. Although 90% of people have heard of units as a concept, only about 13% can calculate them, so it seems we are still very unit illiterate. After so long trying to market 'units' and failing to inspire comprehension - let alone change, is it time to ditch them? 

For some people, calorie information has helped them to cut down on the amount they drink. And I have to admit, it is surprising to see how many calories are in certain drinks. Most people in our research groups are horrified when we present them with this information. They cannot believe that  a glass of wine can have the same amount of calories as four cookies and a pint of lager has the calorific equivalent of a slice of pizza. 

But this will only work if you care about calories and that is a whole new debate. What we know from our research is that women in our groups are particularly supportive of nutritional information on alcohol with many claiming that it would change their purchasing behaviour and consumption habits. They tell us that they may opt for a lower equivalent or stick to just one or two. So is it time for a change? Let us know what you think.