The truth for most Americans is that retirement means living on less. As a result, when planning for retirement, your best friend may be your calculator to help you determine how much you need and what you can afford.

Conventional wisdom among financial planners is that you should retire with at least 70-80 percent of your pre-retirement income.

So before taking the jump from full-time work to full-time retirement, determine what will be your fixed income and expenses, and where you can cut back if needed. Among issues to examine include:

– What benefits are you eligible for from your employer, including group health and life insurances.

– The latest rules and regulations for Medicare and how the new drug prescription plan provisions would affect you.

– The kind of retirement you wish to have.

“How much do you want your lifestyle to change?” said Sally Hurme, attorney in the consumer protection office of the AARP, formerly known as the American Association of Retired Persons.

Ask yourself if you still need as big a house, said John Boraski, a specialist in financial planning for the elderly who is a consulter to Catholic Golden Age, an organization for seniors.

Both advise doing a pre- and post-retirement budget.

Find out where you have flexibility in your current expenses and discover where there is padding, she said.

If Social Security benefits and your company pension are not enough, the next step is to calculate your savings, Boraski said. Ask yourself if you will “live longer than your money” and need to draw regularly from your savings to make ends meet, he said

Does figuring all this out sound daunting?

There is help from government agencies, such as the Social Security Administration and the central Medicare office. Both have toll free numbers and user-friendly Web sites.

The AARP Web site—www.aarp.org/bulletin—has an online calculator to help with the math.

Start with Social Security in determining your fixed retirement income. Check at what age you can fully retire, as this has changed recently. People born after 1937 have to wait beyond 65 before taking full retirement. Partial retirement benefits still kick in at 62, but at a reduced rate.

The Social Security Administration does provide annual estimates projecting monthly benefits the recipient will receive in retirement. These projections are based on several variables and Social Security assumptions including that earning will continue at current levels and that its benefits structure will stay much the same as currently exists.

If you don’t already receive a Social Security annual statement, you can sign up online at www.ssa.gov, by phone (1-800-772-1213) or by mail. The Social Security Administration Web site (www.ssa.gov/planners/calculators.htm) offers three interactive calculators to estimate future benefits.

In examining retirement benefits under any company plans, determine whether you have a fixed-income pension, which gives you a fixed amount monthly for the rest of your life, or a flexible contribution plan, in which the contributions are invested giving you a lump sum at retirement which can be taken in its entirety, used to buy an annuity granting a fixed monthly income for life or withdrawn in regular quotas until the sum is exhausted.

Ask, too, if there are carryover provisions in the health- and life-insurance benefits. Many insurance carriers have conversion provisions which allow continued coverage, but often with lesser benefits at higher costs.

“Read the fine print,” Boraski warned. You may not need as much life insurance if you no longer have dependent children, he said.

Any health insurance plan should dovetail into Medicare, which is available once a person reaches 65. But with new Medicare provisions becoming law in 2003, the situation is in flux. The new provisions include a prescription drug plan and a phased-in introduction of privatized insurance programs. Check with Medicare—www.Medicare.gov, 1-877-267-2323—to keep up to date.

Also note that Medicare is not free. It charges monthly premiums for non-hospitalization benefits and there are deductibles for all services. The latest premiums and deductibles can be obtained at the Web site or by telephone.

Buyer beware when looking for health and life insurance, urged Hurme and Boraski. Both suggested checking with your state insurance commissioner’s office to make sure the company or the agent you are working with has a clean bill of health.

Factor in your savings. You may need to consult a financial adviser to see how best to invest it. This often depends on whether you need to regularly supplement your retirement income or you can afford to let the capital grow and earn interest until you need to draw on it.

Just remember: The more you calculate, the less the risk of surprises.