According to the study, more than eight million adults in England are considered to lack even basic numeracy.
The survey found that this quarter of the population has difficulty in understanding price labels and the sums involved in paying household bills.
Their abilities are at par with those expected of pupils at primary school aged between seven to nine, the survey by Skills For Life found.
In an even more disturbing development, the number of adults in this group is nearly a million more than it was a decade ago, the 'Daily Mail' reported.
Researchers said a further nine million adults have the maths skills expected of a child aged nine to 11.
Those in this group are likely to struggle in calculating change, using train timetables or working out deductions on their pay slip.
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Numbers had risen from 15 million in 2003, when a similar survey was conducted.
The report also revealed that fewer than one in five 16 to 18-year-olds can demonstrate skills equivalent to a grade A to C pass in maths.
"This discrepancy is both puzzling and worrying for everyone involved in education and merits further investigation. Too many adults are struggling with everyday maths," Chris Humphries, chairman of the charity National Numeracy, said.
The survey, which questioned 7,200 people aged 16 to 65, also revealed that more than five million adults