The basic formula: Your earnings history becomes your benefit

Social Security calculates your SSDI benefit by looking at your work history and the wages you earned over roughly 35 years. The agency takes your highest-earning years, adjusts them for inflation, and averages them together. That average becomes your Primary Insurance Amount, or PIA — the number Social Security uses to set your monthly payment.

You do not choose this amount or negotiate it. Social Security's computer system runs the same formula for everyone. The result depends entirely on how much you earned and for how long, not on how much you need or how severe your condition is.

The actual calculation involves several steps, and understanding them helps you know what to expect when you receive your benefit notice.

Key Takeaways

  • Social Security uses your 35 highest-earning years to calculate your benefit, adjusted for inflation to current dollars.
  • The agency averages those years together, then applies a formula that pays a higher percentage of lower earnings and a lower percentage of higher earnings.
  • Your benefit amount is set when you are approved and does not change based on your current needs or living situation.
  • You can request a detailed earnings record from Social Security to verify the years they are counting and spot any missing or incorrect wages.

Step 1: Social Security reviews your complete earnings record

Social Security maintains a record of every year you worked and paid into the system through payroll taxes. This record goes back to 1951 or to the year you turned 18, whichever is later. The agency counts only years where you earned at least a minimum amount — in 2024, that minimum is $1,470, though this figure changes yearly.

If you worked for a government employer that did not pay into Social Security, those years may not count. If you worked under different names or Social Security numbers, some earnings might not be attached to your record. Errors happen: a former employer might have reported your wages under the wrong number, or a wage record might never have been processed.

You can view your own earnings record by creating an account at ssa.gov and logging into "my Social Security." This shows you exactly which years Social Security is counting and what wages they have on file for each year. If you spot an error, you can report it to Social Security with documentation from your employer or old tax returns.

Step 2: Social Security selects your 35 highest-earning years

Social Security does not use every year you worked. Instead, the agency picks your 35 highest-earning years and ignores the rest. If you worked fewer than 35 years, Social Security counts zeros for the missing years — which lowers your average and reduces your benefit.

The agency adjusts each of these 35 years for inflation using a factor called "wage indexing." This means a dollar you earned in 1990 is adjusted to reflect what that dollar would be worth in the current economy. Without this adjustment, people who worked decades ago would receive much smaller benefits than people who worked recently, even if they earned the same amount in current dollars.

For example, if you earned $20,000 in 1995, Social Security does not use $20,000 in the calculation. It adjusts that $20,000 to what it would equal in current dollars, then uses that adjusted figure. The wage indexing factor changes each year based on national wage trends.

Step 3: Social Security averages your adjusted earnings

Once Social Security has your 35 highest-earning years in current dollars, it adds them all together and divides by 420 — which is 35 years times 12 months. This gives you your Average Indexed Monthly Earnings, or AIME. The AIME is the middle step in the calculation; it is not your benefit amount yet, but it is the number Social Security uses to find your benefit.

If you worked fewer than 35 years, Social Security still divides by 420, not by the number of years you actually worked. This is why gaps in your work history — years you did not earn enough to count — reduce your benefit. A person who worked 30 years with good earnings will have a lower AIME than a person who worked 35 years with the same average earnings, because the first person's record includes five zeros.

Step 4: Social Security applies the bend points formula

Social Security does not pay you a percentage of your AIME. Instead, it uses a formula with three "bend points" — dollar thresholds that determine how much of your earnings become your benefit. The formula pays a higher percentage of your lower earnings and a lower percentage of your higher earnings.

In 2024, the bend points are $1,174 and $7,078. Social Security pays 90% of your AIME up to $1,174, then 32% of your AIME between $1,174 and $7,078, then 15% of anything above $7,078. These bend points change every year based on national wage trends.

Here is a concrete example: if your AIME is $3,000, Social Security calculates it this way:

  • 90% of the first $1,174 = $1,056.60
  • 32% of the amount between $1,174 and $3,000 (which is $1,826) = $583.32
  • Total Primary Insurance Amount = $1,639.92

This is your monthly SSDI benefit before any other adjustments. The bend points formula is why someone with very high lifetime earnings does not receive a benefit that is proportionally higher — the formula deliberately replaces a smaller percentage of high earners' income.

Adjustments that can change your benefit amount

Your Primary Insurance Amount is the starting point, but several things can reduce it. If you receive workers' compensation or public disability benefits from a government job, Social Security may reduce your SSDI benefit under a rule called the Government Pension Offset or Windfall Elimination Provision. The reduction varies depending on the other benefit amount.

If you are under full retirement age and you work while receiving SSDI, Social Security reduces your benefit by $1 for every $2 you earn above an annual limit — in 2024, that limit is $23,400. Once you reach full retirement age, this earnings limit no longer applies, though your benefit may be recalculated if your new earnings are high enough to change your record.

If you have not yet reached full retirement age when you are approved for SSDI, Social Security may pay you a reduced benefit. However, most people approved for SSDI before full retirement age receive their full PIA amount, not a reduced one.

How to read your benefit notice

When Social Security approves you for SSDI, you receive a notice that states your monthly benefit amount. This notice does not always explain how that amount was calculated. If you want to see the actual numbers — your AIME, your bend points, your Primary Insurance Amount — you can request a detailed benefit calculation from Social Security.

Call Social Security at 1-800-772-1213 (TTY 1-800-325-0778) and ask for a "detailed earnings and benefit estimate." You can also visit your local Social Security office in person. The detailed calculation shows you every year in your record, the wage-indexed amount for each year, and the formula Social Security used to reach your benefit amount.

If you believe there is an error in your earnings record or in the calculation itself, report it to Social Security as soon as you notice it. Errors in your record can be corrected, but there are time limits for doing so.

Frequently Asked Questions

Can I see how much my SSDI benefit will be before I am approved?

Social Security publishes a "benefit calculator" on ssa.gov that estimates your benefit based on your current earnings record. The estimate is not exact — the actual amount depends on your complete work history and the bend points in effect when you are approved — but it gives you a reasonable idea of what to expect.

What if I have years with no earnings or very low earnings?

Social Security counts those years as zeros in your 35-year average. If you have more than five years with little or no earnings, they will pull down your average and reduce your benefit. There is no way to remove them from the calculation, but you can request that Social Security exclude certain years if you were unable to work due to a medical condition before your onset date.

Does my SSDI benefit increase if I keep working?

If you work and earn more than the annual limit while receiving SSDI, your current benefit is reduced. However, if those new earnings are high enough, they may replace lower-earning years in your record. When you reach full retirement age, Social Security recalculates your benefit based on your complete work history, which could result in a higher amount. You should report all work income to Social Security.

Why is my SSDI benefit different from my spouse's or my parent's?

Each person's benefit is calculated from their own earnings record. Your spouse or parent may have worked different years, earned different amounts, or had different gaps in employment. Social Security also pays family members different percentages of the worker's benefit — a spouse typically receives 50% of the worker's PIA, and a child receives 75% — so even if you have the same earnings record, family members' payments differ.

Can I request a recalculation if I think the amount is wrong?

Yes. Request a detailed benefit calculation from Social Security to see the exact numbers they used. If you find an error in your earnings record, report it with documentation. If the calculation itself is wrong, Social Security can recalculate it. You have a limited time to appeal the amount, so contact Social Security if you believe there is a mistake.