One in three adults struggle with basic maths tasks such as working out change on a shopping trip, according to a new study.
It suggests that adults in England and Northern Ireland perform worse on simple everyday numeracy tasks than those in many other countries.
Researchers from University College London and Cambridge University analysed data from an international OECD survey, which asked 16 to 65-year-olds in 31 nations to answer a series of numeracy-related questions.
The study concluded that between 63% and 68% of those in England and Northern Ireland combined could answer a question on how much change they would get if they were given a set amount of money and asked to buy certain goods.
Between 57% and 62% overall could answer a question on how much they could expect to pay for a given quantity of a product - for example, a third - if they were given the cost of the whole item.
It means that for each of these two questions, around a third, or just over a third, struggled to find a correct answer.
Higher proportions were unable to answer a question related to line graphs and another about discounts on a product.
The study said that "a handful of nations perform comparatively well" across all four questions, including Estonia, Finland and Japan, while at the other end of the scale, adults in Turkey, Chile, Israel, Italy, Spain, England and Northern Ireland "have among the weakest financial skills" across the 31 countries.
Study author Professor John Jerrim, of the UCL Institute of Education, said the research highlights how the nation "is facing a crisis in terms of adults' financial literacy skills".
"We all need to be able to conduct basic financial calculations in order to make rational well-informed decisions," he said.
"This includes how much we should save into our pensions, understanding the financial implications of borrowing money from payday loan sites, through to whether we can really afford to buy a particular house."
Apprenticeships and Skills Minister Anne Milton said: "We do need to improve adult numeracy skills, but it's of note that even in the best-performing countries the test is still failed by one in four people.
"Almost half of the working-age adults in the country currently have the numeracy levels we expect of primary school children. Numbers are part of everyday life - we use them when cooking, shopping, planning journeys, planning meals and budgeting.
"All adults can sign up to take free maths qualifications to learn the skills they need to get on in life.
"They range from entry level all the way up to GCSE, and will include financial calculations and real life scenarios. Last year half a million adults enrolled on a course."