Sleep-deprived workers are costing the UK economy £40bn a year and face a higher risk of death, says a new study.
The calculation is based on tired employees being less productive or absent from work altogether.
Research firm Rand Europe, which used data from 62,000 people, said the loss equated to 1.86% of economic growth.
The main impact was on health, with those sleeping less than six hours a night 13% more likely to die earlier than those getting seven to nine hours.
The study evaluated the economic cost of insufficient sleep in the UK, US, Canada, Germany and Japan.
And while the impact of tired workers in the UK may sound bad, it still ranked better than both the US and Japan which lost the most working days due to lack of sleep.
The cost of sleep deprivation by country:
- US loses 1.2 million working days a year, costing $411bn (£328bn) or 2.28% of GDP
- Japan loses 600,000 working days a year, costing $138bn or 2.92% of GDP
- UK loses 200,000 working days a year, costing £40bn, or 1.86% of GDP
- Germany loses 200,000 working days a year, costing $60bn, or 1.56% of GDP
- Canada loses 80,000 working days a year, costing $21.4bn or 1.35% of GDP
- According to the study, the "healthy daily sleep range" is between seven and nine hours per night.
The report called on employers to recognise and promote the importance of sleep, urging them to build nap rooms.
It said they should also discourage staff from "extended use" of electronic devices after working hours.
Individuals were advised to wake up at the same time each day and exercise during the day to improve their sleep.
"The effects from a lack of sleep are massive. Sleep deprivation not only influences an individual's health and wellbeing but has a significant impact on a nation's economy," said Marco Hafner, a research leader at Rand Europe and the report's main author.
Mr Hafner said small changes could make a big difference, saying if those in the UK currently sleeping under six hours a night increased this to between six and seven hours it would add £24bn to the UK's economy.