How much in savings and investments should you have by age 35 or 45? Or, for that matter, at 65 when you're likely to be near retirement?

If you don't know, you have plenty of company. So many figures are bounced about that it's often difficult for people to know what's the right amount. Many workers end up saving what they can and hoping for the best.

That's why some financial advisers now use a simple yardstick to help clients quickly see how they measure up. It suggests the amount of savings and investments you should have in relation to income at different ages.

For example, at 35 your assets should at least equal your annual income. The formula is by no means gospel, but it's a useful tool to check if you're largely on target, need to save more or should revise your retirement plans.

The idea comes from Charlie Farrell, a Denver investment adviser and author of the book "Your Money Ratios: 8 Simple Tools for Financial Security."

Farrell says financial ratios are used to simplify complicated data for investment professionals analyzing companies. He figured workers could use a similar shortcut for personal finance.

Mari Adam, a financial planner in Boca Raton, Fla., says she uses ratios based on Farrell's book with clients.

"I like it because it is very simple," she says. "When you do retirement planning, it's so complicated, people just don't get it."

The math is easy. Add up all your bank accounts, 401(k)s, individual retirement accounts and other investments. Don't include the equity in your house. That's because, Adam says, "most people still need some place to live and don't take steps to downsize and sell the house."

Younger workers in their mid-20s aren't likely to have a lot of assets built up. What's key for this age group is to get started with saving and investing. Contribute at least enough in a 401(k) to get the employer match if you can't afford to do more now, Adam says. But — and this is crucial — don't forget to increase the contributions 1 to 2 percentage points annually to catch up.

For all other age groups, Adam uses the ratios listed below. Other advisers, she notes, use even more stringent savings targets. Still, if you're not a good saver now, these benchmarks will appear steep:

•Assets at age 35 should equal one to two times yearly gross income.

•Assets at 45 should total three to four times income.

•Assets at 55 should be six to eight times income.

•And at 65, assets should equal 10 to 12 times income.

"These are aspiration levels," Adam says. And if you can't meet them, she says, it doesn't mean you can't retire.

You might be able to get along with having fewer assets if there are other financial factors in your favor. For example, Adam says, you could get by on less if your mortgage is paid off or if you will receive a fat pension or ample Social Security check in retirement. Or, she adds, if you are truly frugal.

But if you're short on savings, you still have time to make changes to improve your finances.

You can squirrel away more, work longer or take a part-time job in retirement. Or delay Social Security benefits until as late as age 70, so you'll get a bigger check. And you can always free up home equity by selling a pricey house and moving to a more modest place.