Source: Social Security Administration.

Social Security pays benefits to millions of Americans, but the program is so complex that many people can qualify for multiple programs during the course of their lifetimes. Determining Social Security eligibility for those various programs can be complicated, as the rules differ greatly from one to the next. Below, you'll find easy-to-understand guidelines to figure out your Social Security eligibility.

Social Security retirement benefits

To be eligible to receive Old Age and Survivors Insurance program benefits based on your own work history, you must have accumulated at least 40 credits, which requires earning a minimum amount of work-related income over at least 10 years.

Once eligible, you can start taking benefits as early as age 62. Full retirement age is currently 66 for those retiring now, and you can delay benefits up to age 70 to get increased monthly payments.

Social Security spousal benefits

Source: SSA.

Spousal benefits are available to those whose spouses have qualifying work histories under Social Security. Spouses also must have been married for a minimum of one year. Divorced spouses are also entitled to receive spousal benefits if they were married for at least 10 years and aren't remarried.

Spousal benefits are also available as early as age 62. Unlike retirement benefits based on your own work history, though, there's no added benefit for delaying spousal benefits past full retirement age. A spouse can also claim spousal benefits at an earlier age if caring for a child under age 16 who receives Social Security benefits.

Social Security children's benefits

Children's benefits are available to those whose parents have qualifying work histories under Social Security. Children have to be either unmarried and under age 18 or in high-school and no older than age 19. Benefits usually continue until the child's 18th birthday, with older high-schoolers losing benefits at graduation or age 19 and two months -- whichever comes first. Disabled children are eligible for benefits if the disability began before age 22, and they can receive benefits indefinitely.

Social Security survivors' benefits

Survivors' benefits are available to certain family members of workers who have qualifying work histories under Social Security. The number of credits necessary depends on age at death, with certain situations requiring as little as six credits during the three years immediately prior to death to qualify. In no case does the number exceed the 40 credits required for retirement benefits.

Source: SSA.

Surviving spouses must have been married for at least nine months prior to death, although exceptions apply for accidental death or death in the line of duty as an active military member. Those who had children with the deceased spouse are often eligible regardless of the length of marriage. Divorced spouses can be eligible if they were married at least 10 years. In general, though, surviving spouses -- whether divorced or not -- can't remarry before age 60 and still claim survivors' benefits. Remarriage at age 60 or afterward has no impact on survivors' benefits.

In addition to surviving spouses, children are also eligible for survivors' benefits. The same age- and disability-related rules for eligibility that apply for children's benefits while the parent is still alive also apply to survivors' benefits, although a shorter work history than that required for retirement benefits can be sufficient depending on age at death.

Social Security disability benefits

Those who have long enough work histories qualify for disability benefits under Social Security. The requirement depends on the age at which you become disabled. Prior to age 24, you need six credits in the three prior years. For those between 24 and 30, you need two credits for every year since age 21. Above age 30, you usually need at least 20 credits in the preceding 10 years, with overall requirements rising by two credits at age 44 and every two years thereafter until reaching the maximum of 40 credits at age 62.

Source: SSA.

Disability recipients have to demonstrate that they can't do the work that they did before, that they can't adjust to other work because of their medical condition, and that the disability will last at least a year or be terminal. Benefits aren't available for partial disability or short-term disability.

Social Security disability family benefits

If you're disabled, your family can also claim benefits under certain conditions. Your spouse can collect benefits upon reaching age 62 or when caring for a child who is under the age of 16 or disabled. Children are also eligible under the same guidelines that apply to children's benefits under the retirement program of Social Security.

Supplemental Security Income benefits

In addition to Social Security, Supplemental Security Income or SSI is available to those who are 65 and older or who are blind or disabled. In order to qualify for SSI, you must have limited income and financial resources, and you must also meet certain citizenship and residency requirements. You also have to exhaust other available benefits or payments to which you're entitled.

In general, if you have a net worth of more than $2,000 as an individual or $3,000 as a couple, you won't qualify for SSI. But those amounts don't include your home, household goods, one vehicle, and certain other items. Also, income above certain levels will reduce or eliminate SSI eligibility.

The Social Security program is complicated, with many different facets. By knowing all the Social Security eligibility rules, though, you can ensure that you'll receive everything you're entitled to get from Social Security.