Employees surveyed for the study reported that they worked an average 5.4 hours of unpaid work a week, including an extra 6.2 hours for full-time workers and 4 hours for casuals and those in part-time positions.
And dissatisfaction with work hours was high, with almost half saying they wanted to work more or fewer hours.
The institute estimates that employers are benefiting from $11,055 in unpaid overtime from the average worker, with the period worked equivalent to an extra seven 38-hour weeks a year of free labour.
The study's author, Centre for Future Work researcher Fiona Macdonald, said the findings, based on responses from 1640 people, including 1000 in paid work, showed that despite high demand for workers, the labour market was still failing to deliver the kind of work hours that many wanted and the result belied the idea that workers had the upper hand.
Dr Macdonald said there was significant mis-match between work conditions and the needs of workers.
"We've got many workers, especially casuals in insecure jobs, wanting more hours," she said. "At the same time, employers are more likely to demand long hours, including large amounts of unpaid overtime, from full-time workers."
The findings come amid evidence that worker demand for work from home arrangements remains high.
An analysis of employment ads by job search company SEEK has found that proportion of vacancies that include work from home provisions leapt from 1.6 per cent just prior to the pandemic to peak of 11 per cent in April and 10 per cent in October.
SEEK senior economist Matt Cowgill said work from home was "still a feature of our labour market".
While the overall proportion of jobs offering WFH arrangements has declined slightly, Mr Cowgill said this was largely due to changes in the composition of positions being advertised, including a relative decline in white collar ads.
He said the WFH job ad rate in most industries remained "at or near a record high".
Dr Macdonald said employees were agreeing to greater hours because of cost of living pressures, "giving their bosses a free kick because many of those hours end up being unpaid".
She said greater protections for workers, like those proposed in the federal government's Closing the Loopholes legislation, were "an important priority for improving labour market outcomes".
Sign up for our newsletter to stay up to date.