Working overtime costs you money. Even a meagre 45 minutes a day on a salary of $60,000 will cost you $5,625 each year. That's enough to pay for an overseas holiday.

If that's not enough to make you sit back and think, then enter your own details in the Unpaid Overtime calculator at the website Thisismoney.co.uk/calculators (just ignore the pound sign and pretend it's a dollar sign).

If you're one of those people who regularly works an extra eight-hour day at the weekend, then on a $60,000 salary you could be throwing away $12,000 each year, because you should really be paid $72,000 for the amount of work you're doing. The What To Tell Your Boss section results are an eye opener for salaried staff.

While few of us think of our salaries as an hourly amount, the calculator tells you that a $60,000 salary breaks down to $28.85 an hour. Make that a 60 hour week and you're being paid just $19.03 an hour.

Unfortunately walking out the door at 5pm doesn't necessarily get you off the hook these days. Technology such as mobile phones, text messaging, email and laptops, mean many people work at home after hours, lengthening working days and intensify work.

"What's the point of working for free," says TV3's Money Man Brendon Johnson. "Overtime is a mug's game."

The former Royal Marine takes a sergeant-major approach to personal finance and says if you want to get ahead financially walk out of the door on time and make extra money on the side or educate yourself so that you can get a promotion.

"I think people just aren't confrontational enough."

These days most contracts require salaried employees to work from time to time outside core hours, says John Nevill, principal at employment agency Numero. However, working long hours doesn't automatically equal being efficient, he adds.

"You will often find that some of the highest performers are mums who have come back to work and have to stick to their hours," says Nevill. Knowing that they only have limited time they concentrate on getting the job done. On the other hand some employees spend hour after hour at the coffee machine, with little to show for their apparently long hours.

If you choose to stick to your hours at a firm with a culture of long working hours it's likely you may get ostracised, says Nevill. Even if you're not going to get a promotion in-house, you can advance your career by moving to a new company. They're not to know you're a clock watcher.

It's also important in today's tight labour market for businesses to keep an eye on staff overtime. If the time expectations on staff are what Nevill calls the "unfair category" then staff members are going to want to move on.

John Wenger director for performance consultants Quantum Shift says firms that have a culture of chronic overtime need to take a step back and take a long hard look at the company culture. "Employees get burnt out and staff turnover increases."