Some 13.5m adults in the UK become stressed out when asked to carry out basic sums, research suggests.
People use maths up to 14 times a day, the study said
And 10m adults lack confidence in using literacy skills, analysis of questionnaires completed by 1,001 adults for Learndirect suggests.
The most common stress-raisers were working out cooking times, writing notes for the boss and tough spellings.
The study also suggested people have to use maths skills up to 14 times daily and literacy skills 23 times a day.
Some 27% of the 1,001 adults aged 16 to 65 asked said they lacked confidence in their basic maths skills.
And about one in five (21%) said they were not confident in their basic English skills in the survey for Learndirect, the UK's largest provider of basic skills training.
The researchers then applied these percentages to UK population figures from the Office of National Statistics to arrive at the numbers of those lacking in basic skills.
Participants were also asked which situations involving calls on their maths or literacy skills made them feel stressed.
The questionnaire study was backed up by more detailed research with three volunteers who kept a numeracy and literacy diary for three days.
They were also supplied with blood pressure and heart rate monitors which they used to record any changes when they got into stressful situations.
Calculating best foreign currency rates
Answering a tricky maths question in a pub quiz
Working out cooking times
Unfamiliar words with difficult spellings
Using grammar or apostrophes correctly
Hand-writing notes for their boss
Reading instructions on a label
On average, participants' blood pressure rose by about 40% and heart rate by a quarter when they became involved in such stressful situations.
They also reported confusion, nervousness, anger and bad temper when they became stressed by their lack of skills.
The results of the research is being published as Learndirect launches its own skills challenge.
This is an interactive web quiz hosted by TV maths expert Johnny Ball and presenter Eammon Holmes and is available on the Learndirect website.
Learndirect's Sally Coady said: "We don't realise just how many times we apply maths and English to everyday situations.
"Almost 8 million people would ask someone else to do the task, rather than tackle the problem head on to avoid embarrassment.
"The quiz is an opportunity to think about how you can brush up on your maths and English if you need to."