Many adults struggle with basic sums and rely on a calculator to add and subtract, new research suggests.
Around one in six (15%) say they find the subject difficult, and sometimes feel embarrassed by their lack of maths skills, according to a poll commissioned by BAE Systems.
The findings show that almost a fifth (18%) of more than 2,000 adults surveyed admitted that they find sums difficult, and usually use a calculator to help them with addition and subtraction.
It comes as a separate study by the National Numeracy charity found that many UK adults feel they were badly prepared at school for the maths they will need in everyday life.
The first survey, published to mark the launch of BAE Systems' nationwide Schools Roadshow, reveals that more than a third of adults (38%) say their job requires them to do a small amount of maths each day, with half (50%) of those polled agreeing that some of life's most important decisions require the subject.
It also suggests that many adults did not enjoy their early experiences of maths, with 30% admitting they found the subject "uninspiring" at school and one in four (24%) saying maths was their least favourite lesson.
The poll asked adults to complete a random multiplication test, and found that the 11 times table is the most difficult for people to master - around one in five (19%) of those who answered questions on this times table got some of the answers wrong.
Some 2% of the adults questioned said that they tend to use a calculator to add or subtract numbers higher than 10, 3% use a calculator for numbers higher than 20, 7% for numbers higher than 50, and 13% for numbers higher than 100, the poll found.
BAE Systems group managing director Nigel Whitehead said: "Maths and science are crucial to the success of Britain's youth and our nation's future but it appears that we start to lose arithmetic skills as we grow up.
"Good maths skills open up so many opportunities both personally and professionally. With increased competition for jobs it is more important than ever that students keep working at maths and the sciences - continued study of these subjects will likely lead to rewarding and sustained employment in the engineering and technology sectors."
More than a third (37%) of UK adults would like to improve their maths skills, according to the National Numeracy study.
It raises concerns that many adults do not feel they have the maths skills they need.
Almost a quarter (22%) said they were not well prepared at school to use maths in everyday life, while more than two-thirds (67%) said the subject is important to them in their daily lives.
National Numeracy chief executive Mike Ellicock said: " Being numerate means being able to use numbers and think mathematically, which is essential for so many aspects of everyday life and work, and this poll suggests that many people recognise that.
"We are developing the National Numeracy Challenge to respond to this and enable everyone to start to improve their maths. To anyone tempted to say 'I can't do maths', we say 'Yes, you can'."
The BAE Systems poll, conducted by You Gov, questioned 2,016 adults between March 2 and 6 and the National Numeracy survey, also conducted by YouGov, questioned 2,151 adults between February 27 and March 1.