There is no simple formula. But experts say the sooner you start to think about your retirement expectations, the better.

When do you want to retire, and how many years will you want to spend in retirement? A male is now expected to live to 75.7, and a female to 81.4. So plan on 20 to 25 years in retirement if you're female (if retiring at 65) and a bit less if you are male.

What sort of lifestyle do you want in retirement? A common target is 60 to 65 per cent of your pre-retirement income (bearing in mind that you won't have to pay expenses such as commuting, work clothes and, hopefully, mortgage repayments by then, and you may be entitled to a part pension and/or tax concessions). So if you earn $50,000 now, a starting point might be to think of a retirement income of about $30,000 a year.

OK, so what's next?

This is where it gets tricky. You need to work out the level of money you must save to give you that retirement income - and that depends on all sorts of variables, such as inflation, investment returns and tax.

You'll need to revise this regularly - maybe with a financial planner. The good news is that there are some ready reckoners you can use to work out how much money you need.

The reckoner on the takes into account your retirement age and life expectancy and shows the amount of money you need to save to provide yourself with various levels of retirement income, taking into account various levels of investment return.

It shows that if you want to retire at 55 on an annual income of $30,000 you'd need a lump sum of $528,775 if your retirement money earns only 3 per cent. But lift those earnings to 9 per cent and you'll need a lump sum of only $296,164.

Retiring at 65? For that same $30,000 income you need a lump sum of $400,945 if your money is earning 3 per cent, but $258,501 if it earns 9 per cent.

Money columnist Noel Whittaker has a simpler rule of thumb: $100,000 of savings for each $8,000 of retirement income. So for $30,000 income, you'd need about $375,000. Remember, these figures are in today's dollars (May 2000), so allow for inflation.

Sounds horrible. So how much should I save?

The glib answer (glib because it is used so widely) is that you need to save 15 per cent of your salary over a full working life to get a retirement income of about two-thirds of your pre-retirement salary.

The truth is that few people do that. There are some good super calculators on Web sites such as www.national.com.au, www.superannuation.asn.au, www.btfunds.com.au and www.amp.com.au, but the general rule is that you should be trying to save more than 15 per cent if you're older - less if you have other investments that can be used for your retirement living.

It doesn't all have to be in super?

While financial planners argue that super is a tax-effective way of saving for your retirement, they also look at the big picture. If you have other investments, or if you are prepared to sell your home when you retire and buy something cheaper, that can all be included in your retirement savings strategy.