You'll often hear that if you work and pay into Social Security during your lifetime, you'll be eligible for benefits once you're ready to retire. But what if you never worked, or only spent a handful of years in the workforce?

It may be that you didn't have much of a career because you opted to stay home and raise children. Or, you may have experienced health issues that kept you from holding down a job.

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The good news is that you may be eligible for Social Security as a retiree even if you never worked. That's because the program pays spousal benefits to people who are or were married to eligible recipients.

Figuring out what spousal benefit you're entitled to could help you better plan for retirement. So it's a good idea to run those numbers and see what they look like.

What the average Social Security spousal benefit looks like today

These days, the average monthly Social Security spousal benefit for wives is about $915, while the average benefit for husbands is about $714. But there's a pretty easy way to estimate what spousal benefit you may be eligible for.

First, figure out when you intend to claim your spousal benefit. If you're married, you'll have to wait until your spouse files for Social Security to get a spousal benefit. If you're divorced, you can claim a spousal benefit before your ex does.

You can file for Social Security spousal benefits as early as age 62. But that will reduce the amount of money you receive each month.

If you wait until your full retirement age (FRA) to claim your spousal benefits, you won't face a reduction. You also won't gain anything financially by claiming your spousal benefits after FRA, so whether yours is 66, 67, or somewhere in the middle, that's really the latest age you should be aiming to sign up.

From there, you can have your spouse get an estimate of their monthly benefit by checking their most recent earnings statement on the Social Security Administration's website. Assuming you claim your spousal benefits at FRA, you'll be entitled to 50% of the amount your spouse is eligible for. So if they're looking at $1,900 a month at FRA, that puts your spousal benefit at $950 if you file at your FRA.

When you have an earnings history of your own

You might assume that if you earned enough to collect Social Security based on your own income record, then you won't be entitled to spousal benefits as a retiree. But that's not true.

Social Security will actually pay you the higher of your benefit or your spousal benefit. So if you're eligible for $1,500 a month on your own earnings record but your spouse is in line for $3,100 a month from Social Security, your spousal benefit would give you $1,550. And in that case, you're entitled to the extra $50 beyond what your own benefit would pay you.

All told, spousal benefits from Social Security could be a real financial lifeline in retirement, especially if you're not coming in with a ton of savings. So in the course of your planning, read up on the rules of spousal benefits so you know when to claim them. And have your spouse get an estimate of their monthly benefit so you know how much spousal income to expect.