The short answer
A spousal benefit is worth up to 50% of what your spouse would receive at their full retirement age. You do not get it on top of your own retirement benefit - Social Security pays the higher of the two, not the sum. Divorced people can qualify on an ex-spouse's record if the marriage lasted at least 10 years.
What the benefit is worth
The maximum spousal benefit is half of your spouse's primary insurance amount - the figure they would receive at their own full retirement age. That ceiling is fixed at half regardless of anything else, and reaching it requires you to claim at your own full retirement age.
One detail catches people out. If your spouse delays claiming past their full retirement age, their own benefit grows with delayed retirement credits, but your spousal benefit does not. It is still calculated on the full retirement age figure, so waiting does not raise the spousal half.
You do not receive both benefits
If you qualify for a retirement benefit on your own record as well, Social Security does not pay both. You receive your own benefit, topped up to the spousal amount if the spousal amount is higher. In practice that means the spousal benefit only adds something when your own record is worth less than half your spouse's.
This is why the calculation is worth doing rather than assuming. Someone with a modest work record of their own may find the two are close, and someone with almost no earnings history may find the spousal benefit is most of their income.
Claiming early reduces it permanently
You can claim a spousal benefit from age 62, and doing so reduces it for life. The reduction is steeper in the first three years before full retirement age than in any years beyond that, and it does not reverse when you later reach full retirement age.
There is one exception worth knowing. If you are caring for your spouse's child who is under 16 or disabled, a spousal benefit can be paid regardless of your age, and the early-claiming reduction does not apply in the same way.
Divorce does not necessarily end it
A divorced person can claim on an ex-spouse's record if the marriage lasted at least 10 years, they are currently unmarried, and they are at least 62. The ex-spouse is not notified, their own benefit is unaffected, and a new spouse of theirs can claim as well.
If the divorce was at least two years ago, you can claim even if your ex-spouse has not claimed yet, provided they are old enough to qualify. Remarrying generally ends eligibility on the former spouse's record.
Public pensions no longer cut it
For decades a pension from work that did not pay into Social Security could sharply reduce or wipe out a spousal benefit, under a rule called the Government Pension Offset. The Social Security Fairness Act repealed that offset, effective for benefits payable from January 2024.
If you were told years ago that a teacher's, firefighter's or other public pension made a spousal benefit pointless, that advice may no longer hold. It is worth checking again with the Social Security Administration.
How to apply, and what to have ready
You apply to the Social Security Administration online, by phone or at a field office, and you can apply up to four months before you want benefits to start. A spousal claim is not automatic: if you are already receiving your own retirement benefit and later become entitled to a higher spousal amount, you have to claim it.
Have your marriage certificate to hand, and a divorce decree if you are claiming on a former spouse's record - the dates on it are what prove the 10-year rule. You will also need your spouse's Social Security number, and your own birth certificate if Social Security does not already hold it.
What our calculator works out
Our spousal calculator works out the share of your spouse's full retirement amount you would receive at the age you plan to claim, and shows how much the early-claiming reduction costs at each age between 62 and your full retirement age.
What this does not tell you
This is an estimate, not a decision. The Social Security Administration decides entitlement using your actual earnings records and marital history, and only they can confirm what your spouse's full retirement amount is.
The calculator covers the ordinary spousal case. It does not model survivor benefits, benefits for a spouse caring for a young or disabled child, or the interaction with your own retirement benefit where both records are substantial.
Official sources
What you can do next
Find out what your spouse's benefit would be at their full retirement age, then compare half of it with your own estimate. If your own record is worth less than that half, the spousal benefit is the one that matters, and the age you claim is the biggest thing still in your control.