Three out of four drinkers have no idea how many units of alcohol are in a glass of wine, a government-sponsored survey has found.
Despite more than four out of five people claiming they knew what a unit of alcohol is, many underestimated how much was in the alcoholic drinks they consume, the YouGov poll found.
Only 23% of people knew how many units are in a glass of wine and 55% thought a glass contains two units when it actually contains three.
More than a third (35%) of people did not know that an average pint of beer contains two units, while nearly three out of five (58%) did not know a double gin and tonic also contains two units.
Launching a new "Units" campaign which aims to tell drinkers how many units are in their drinks, public health minister Dawn Primarolo said: "Glass sizes have grown larger and the strength of many wines and beers has increased, so it's no wonder some of us have lost track of our alcohol consumption.
"This campaign is all about helping people understand how many units are in their favourite drinks, and helping them to keep an eye on their intake for the good of their long-term health."
The YouGov survey also found that while most women (64%) knew that their recommended daily intake is 2-3 units, just half of the men knew their equivalent guidelines are 3-4 units a day.
Unit awareness also appears to get worse with age: 32% of drinkers aged 18-24 correctly said that a large glass contains three units, compared to just 18% of drinkers over 55.