The short answer
A widow or widower who has reached full retirement age generally receives 100% of what the person who died was entitled to. Claiming at 60, the earliest ordinary age, cuts that to about 71.5%. You do not receive a survivor benefit and your own retirement benefit together, but unlike a spousal benefit you may take one now and switch to the other later.
Up to the whole benefit, not half of it
This is the first thing that separates a survivor benefit from a spousal one. A spousal benefit is worth up to half of what a husband or wife would receive at their full retirement age. A survivor benefit, claimed at your own full retirement age or later, is generally worth 100% of what the person who died was entitled to, including any delayed retirement credits they had earned by waiting.
One rule works the other way. If your spouse had already claimed early and was receiving a reduced payment, your survivor benefit is generally limited to what they were actually getting, though it is not cut below 82.5% of their full retirement amount. A decision your spouse made years ago can therefore still set the ceiling on yours.
Sixty is the earliest ordinary age, and it costs you
A surviving spouse may generally claim from age 60, two years earlier than a retirement benefit. The reduction at 60 is steep: about 71.5% of the full amount, rising gradually toward 100% as you approach your full retirement age. Every month of waiting between those two points adds something.
Two groups may start sooner. A surviving spouse who has a disability may claim from 50, also at about 71.5%. A surviving spouse of any age who is caring for the deceased's child under 16 may receive 75%, and that payment does not depend on the survivor's own age at all.
Your full retirement age for survivors is its own number
Social Security publishes a full retirement age for survivor benefits that falls between 66 and 67, and it is not always the same as the full retirement age for your own retirement benefit. Two people born in the same year can have two different dates, one for each kind of payment.
It matters because the entire reduction schedule is measured from it. Reading a retirement full retirement age off a chart and assuming it governs a survivor claim is one of the more common ways to misjudge this benefit by several percentage points.
You may take one benefit now and the other later
You cannot collect a survivor benefit and your own retirement benefit at the same time. Social Security pays the higher of the two rather than the sum, which is true of spousal benefits as well. What is different here is that survivors are allowed to switch.
A widow or widower may start a survivor benefit at 60 and move to their own retirement benefit at 70, when their own has grown as large as it will get, or do the reverse when their own record is the smaller of the two. Which order leaves you better off depends on the two amounts and on your own circumstances, and it is worth working out before you file.
Marriage, divorce and remarriage
A surviving spouse generally has to have been married to the person who died for at least nine months, with exceptions including an accidental death. A divorced person may qualify on an ex-spouse's record on the same terms as a widow or widower if that marriage lasted 10 years or more.
Remarriage is where people give up money they did not have to. Remarrying before 60, or before 50 if you have a disability, generally ends eligibility on the earlier record. Remarrying at or after those ages does not affect it at all.
Children, parents and the one-time payment
A survivor benefit is not only for a spouse. An unmarried child of the person who died may generally receive 75%, up to age 18, or older while still in secondary school or if a disability began before 22. Dependent parents aged 62 or over may qualify as well. A family maximum limits the total that can be paid on one record.
Separately, Social Security pays a one-time lump sum of $255 to a surviving spouse who was living with the person who died, or in some cases to an eligible child. It has to be claimed, generally within two years of the death, and it is not paid automatically.
What our calculator works out
Our survivor calculator works out the share you would receive. It takes the deceased worker's benefit amount, your age at claiming and your survivor full retirement age, and applies the reduction schedule Social Security publishes, including the cases where a different rule applies such as caring for a child under 16.
What this does not tell you
This is an estimate of one payment, not a claim decision. Social Security holds the earnings record and makes the determination, and a survivor claim generally cannot be started online, so treat the figure as a way of going into that conversation knowing roughly what to expect.
The calculator does not model the family maximum when several people claim on one record, whether switching benefits later would leave you better off, or the earnings test, which can withhold part of a survivor benefit if you claim before full retirement age and keep working.
Official sources
What you can do next
If your spouse has died, or you are weighing a claiming decision of your own, start with the amount and the age. Then contact Social Security, because a survivor claim is one of the few that generally cannot be filed online.