The average employee in Wales works an extra 6.2 hours per week - adding up to an extra £735m-worth of value to the Welsh economy.
"That's a huge amount of hours," said Rhianydd Wiliams from Wales TUC.
"We're asking employers to recognise these extra hours and maybe looking at better ways of managing time within the office so that people feel they can leave on time or have a proper lunch break."
More top news
A cloudy night with drizzle in places. Heavier rain and strengthening winds arriving tomorrow afternoon.
Nazar gave up a career as a property developer to become a humanitarian, raising more than £200,000 for good causes around the world.
Terence Francis was reported missing from his home in Haverfordwest yesterday.