Social Security can seem like a black box: you pay into it for decades, and one day a number appears on your statement. In fact, the formula is published and follows the same steps for everyone. Knowing how it works can help you spot mistakes in your earnings record and understand how decisions such as working longer affect your benefit.
Step 1: Earning enough credits
To qualify for retirement benefits, you need 40 credits. You earn credits by working and paying Social Security taxes. In 2026 you earn one credit for each $1,890 of earnings, and in 2027 one credit for each $1,970, up to four credits a year. Most people reach 40 credits after about 10 years of work.
Credits only decide whether you qualify. They do not set the size of your benefit.
Step 2: Your highest 35 years
Social Security looks at your entire work history and picks the 35 years in which you earned the most. Only earnings up to the yearly maximum taxable amount count; the cap is $184,500 in 2026 and $192,300 in 2027.
If you worked fewer than 35 years, the missing years count as zeros. That is why working an extra year or two late in your career can raise your benefit: a good year can replace a zero or a low-earning year from early in your career.
Step 3: Adjusting for wage growth
A dollar earned in 1985 bought more than a dollar does today, and wages have grown a great deal since then. So Social Security "indexes" each year's earnings to account for the general rise in wages. Earnings up to the year you turn 60 are adjusted this way. Earnings after 60 are counted at face value.
Step 4: Your average monthly earnings
The adjusted earnings for your 35 highest years are added together and divided by 420, the number of months in 35 years. The result is your average indexed monthly earnings, or AIME.
Step 5: The benefit formula
Social Security applies a three-part formula to your AIME to get your primary insurance amount, which is the benefit you receive at full retirement age. For people who turn 62 in 2027, the formula is:
- 90% of the first $1,340 of average monthly earnings,
- plus 32% of earnings between $1,340 and $8,077,
- plus 15% of earnings above $8,077.
The dollar limits in the formula, called bend points, are set by the year you turn 62 and rise each year with average wages. Because the first slice is replaced at 90% and the last at 15%, the program replaces a much higher share of earnings for people with lower lifetime pay.
Step 6: Adjusting for your claiming age
The amount from the formula is what you would receive at full retirement age. If you start earlier, it is reduced; if you start later, up to age 70, it grows. Read when to claim Social Security for the details.
A simple example
Suppose your average indexed monthly earnings are $5,000 and you turn 62 in 2027:
- 90% of $1,340 = $1,206.00
- 32% of the next $3,660 ($5,000 minus $1,340) = $1,171.20
- Total: about $2,377 a month at full retirement age, before rounding and cost-of-living increases.
Check your earnings record
Mistakes happen. An employer may report wages under the wrong number, or a year of self-employment may be missing. Review the earnings history in your Social Security statement each year. If something looks wrong, gather W-2 forms, tax returns or pay stubs and contact Social Security. It is much easier to fix an error soon after it happens than decades later.
The my Social Security account guide explains how to see your statement online.
