According to a Health and Social Care Centre report, the average British woman thinks they weigh 10st 11lbs when their actual weight is 11st 3lbs, the Mirror reported.
The report also shows the gap between perception and reality was biggest among women between 35 and 39.
They think they are nearly 8lbs lighter than they actually are Men underestimate their weight by about 3lbs, the report said.
They mistakenly think they weigh 13st on average, when they actually weigh 13st 3lbs.
It is not known why women underestimate their weight more than men.
It is the first time the Health and Social Care Centre has examined the issue. More than 8,000 adults were quizzed about their perceived height and weight before their actual measurements were recorded by researchers.
Parents were also asked whether they thought their child was the about the right weight, too heavy or too light before their child was measured Incredibly, nearly half of parents of obese kids thought their child was “about the right weight,” according to the report Health Survey for England.
And four out of five parents of overweight children thought their son or daughter was “about the right weight.
“This survey gives a brand new insight into how the average adult in England has a different idea of their weight compared to what the scales actually show,” HSCIC chief executive Tim Straughan said.
“Women appear to misjudge their weight more than men – with women in their late thirties in particular underestimating their weight by nearly 8lb,” he added.
If peoples’ own estimated weight and height were used to classify their weight, 17 percent of men and 20 percent of women would be classified as obese.
But the reality is much worse. Actual measurements put the figures at 24 percent and 26 percent respectively.
The report found that while people are generally close to knowing their actual height, their perception of weight is far less accurate.