Most Australian McDonald's workers are still in school, thrilled to be earning a buck in their first real job. But for others who rely on the work, meagre pay makes it tough to pay the bills.

More than two-thirds of the fast food giant's workers are paid less than the basic wages safety net, known as the Fast Food Award.

Even a conservative analysis finds McDonald's workers nationally are underpaid tens of millions of dollars a year due to the controversial union-brokered agreement.

Brigid, 19, WA

Brigid Forrester, an ex-McDonald's employee from Perth, worked up to four shifts a week, including Sunday nights from 4pm to 10pm.

Hired as a casual, the 19-year-old's pay was $20 an hour. If she had been covered by the award, her normal hourly rate would have been roughly the same, but would climb to as much as $23 in the evenings and almost $30 on Sundays.

"The weekends were tiring, terrible shifts to work," she said. "I would always joke with people about how bad our pay was, but I was struggling to pay rent, and I have to pay for petrol and for parking at university."

Ms Forrester said she quit McDonald's in November after the store management attempted to move all the casual staff into part-time positions, meaning she would lose her casual loading and her take-home pay would be reduced further.

"I just couldn't afford to have my pay go down any more," she said. "I said I didn't want to become part-time, and soon, they dropped my hours abysmally. I couldn't afford to keep working there."

Megan, 18, VIC

It's Saturday night in Melbourne and hungry crowds straight from the footy are looking for a feed.

The staff at the McDonald's front counter are all young and almost all casuals.  It's 18-year-old Megan's* fourth shift this week.

"I'm trying to pay for half of my university fees, but that's not going so well at the moment, because of how bad my pay is," she said.

"If you look at other hospitality jobs, they get paid higher rates on the weekend, but we get nothing."

Megan juggles university with weekday and weekend work starting as early as 7am, and evening shifts knocking off around midnight.

If she were paid according to the award – the industry's wages safety net – Saturday night shifts would attract generous penalty rates. Under the McDonald's agreement, she won't earn more than $17 an hour unless it's a public holiday.

"It's hard working on weekdays, going to and from uni, and then weekends too but not getting any penalty rates," she said.

Hugo, 21+, NSW

Hugo* has worked on-and-off at a McDonald's for several years. He recalls a 2009 staff meeting  when company and union representatives encouraged workers to sign onto a new agreement that was pitched as a weekly "$10 upfront wage increase".

"People who relied on the penalty rates the most, the people who actually needed them, lost out," he said.

A part-time staff member, he earns $20 an hour regardless of whether it's a weekend, weekday or evening shift. The only higher rate is an extra 10 per cent for the few times he works between 1am and 5am.

If he were receiving award-rate pay, his base $20 an hour would become $22 between 9pm and midnight, $23 between midnight and 6am. On weekends, he would get $25 on Saturdays and $30 on Sunday.

Hugo said working at McDonald's could be a good job for young teenagers.

"But for someone who wants to be able to afford to live in Sydney, it's definitely not good enough."