Q: Mr. K asks: “I am 56 years old. I worked for the state of Florida until April 2007 when I chose an early regular retirement benefit. I have not worked since. Before April 2007 I had continuous Social Security credits from the age of 16 save for four years during high school and college years.

“My question is: If I do not earn any further Social Security credits between now and age 62 how will my SS benefits be calculated? If I become totally disabled (heaven forbid) how will my SSDI benefits be calculated if I have no further earnings between now and 62?

“If I return to work and have SS earnings less than my previous wage between now and age 62 how will SS and SSDI benefits be calculated? Also, will I still be eligible for Medicare benefits at age 65? Thank for your assistance and expertise.”

A: Social Security benefits are based on earnings averaged over most of a worker’s lifetime. Your actual earnings are first adjusted or “indexed” to account for changes in average wages since the year the earnings were received. Then we calculate your average monthly indexed earnings during the 35 years in which you earned the most. We apply a formula to these earnings and arrive at your basic benefit, or “primary insurance amount.” This is the amount you would receive at your full retirement age, for most people, age 65. However, beginning with people born in 1938 or later, that age will gradually increase until it reaches 67 for people born after 1959. For more information, see “Full Retirement Age is Increasing” at www.socialsecurity.gov/pubs/ageincrease.htm.

As you can see from the above, the benefit computation is complex and there are no simple tables that we can present that will tell you how much you will receive. However, there are several ways you can determine an estimate of your retirement benefits:

* Use our new retirement estimator at www.socialsecurity.gov/estimator/ which produces estimates that are based on your actual Social Security earnings record.

* Request a Social Security statement. Make your request over the Internet at www.socialsecurity.gov/statement/ and we will mail you a detailed report of your lifetime earnings and an estimate of retirement, disability and dependent benefits.

* Compute your own benefit estimate using a program that you can download for your PC at www.socialsecurity.gov/OACT/anypia/anypia.html. A version for the Mac is available at www.socialsecurity.gov/OACT/anypia/download.html.

* Use our online calculator at www.socialsecurity.gov/retire2/AnypiaApplet.html and enter your own data.

* See examples of how benefits are computed at benefit calculation examples at www.socialsecurity.gov/OACT/ProgData/retirebenefit1.html.

* See our publication, “Your Retirement Benefit: How It Is Figured” at www.socialsecurity.gov/pubs/10070.html.

Generally, we advise people to file for Medicare benefits three months before age 65. Remember, Medicare benefits can begin no earlier than age 65.

The number of work credits you need to qualify for disability benefits depends on your age when you become disabled. Also, the credits must have been earned within a certain time period. Generally, you need 20 credits earned in the last 10 years, ending with the year you become disabled. Younger workers may qualify with fewer credits. For example:

— A worker who becomes disabled before age 24 needs to have earned six credits in the three-year period ending when disability starts.

— A worker who becomes disabled between age 24 to age 31 needs to have credits for half the time between age 21 and the time disability starts. If disability starts at age 27, the worker would need credit for three years of work (12 credits) out of the past six years between age 21 and 27.

For additional information, we recommend that you read our publication, “Disability” (SSA Publication No.05-10029) at www.socialsecurity.gov/pubs/10029.html.

Note: Social Security offices will be closed on Dec. 25 and Dec. 26 in observance of Christmas.

Get answers to your Social Security questions each Thursday from Social Security District Manager Eleanor Jones. Submit questions to her attention by writing to Business Editor John Vass Jr., Chattanooga Times Free Press, P.O. Box 1447, Chattanooga, TN 37401-1447, or by e-mailing him at jvass@timesfreepress.com.