The Basic Formula: Your Primary Insurance Amount

Your monthly SSDI payment is based on your Primary Insurance Amount (PIA), which Social Security calculates from your lifetime earnings record. The agency does not straightforward divide your total earnings by the number of months you worked. Instead, it uses a specific formula that weights your highest-earning years more heavily and applies a bend point adjustment that reduces the percentage of income replaced at higher earning levels.

Social Security pulls your earnings history from your Social Security tax contributions (FICA taxes) going back to age 21 or 1951, whichever is later. The agency then selects your 35 highest-earning years, adjusts those years for wage inflation using a national wage index, and averages them across 420 months (35 years × 12 months). This average is called your Average Indexed Monthly Earnings (AIME).

Once Social Security has your AIME, it applies the bend point formula. The bend points change each year and are published by Social Security in January. For 2024, the bend points are $1,174 and $7,078. Your PIA is calculated by taking 90 percent of your AIME up to the first bend point, 32 percent of the amount between the first and second bend point, and 15 percent of anything above the second bend point. The sum of these three amounts is your PIA, which becomes your monthly SSDI payment if you have no other factors affecting it.

Key Takeaways

  • Your monthly payment comes from your Primary Insurance Amount, which is based on your 35 highest-earning years adjusted for wage inflation.
  • Social Security uses a three-tier formula with bend points that give you a higher percentage replacement on lower earnings and a lower percentage on higher earnings.
  • Your actual payment may be reduced if you earned income while under full retirement age, received workers' compensation, or have other government pensions.
  • You can request a detailed earnings record from Social Security to verify the years and amounts used in your calculation.
  • The bend points and the entire PIA formula change each year, so your payment amount is recalculated annually even if you do not report new earnings.

How Social Security Adjusts Your Earnings for Inflation

Social Security does not use your actual dollar amounts from 1985 or 1995. Instead, it adjusts your earnings from each year using the National Average Wage Index, which measures how much the average American worker earned that year. This adjustment is called wage indexing, and it ensures that your benefit reflects your earnings relative to the economy at the time you worked, not the raw dollars you received decades ago.

The agency applies the wage index only to your earnings up to age 60. Earnings after age 60 are used at their actual dollar value without indexing. This means if you worked and earned income between ages 60 and 62, those years count toward your 35-year average at face value, which can either help or hurt your benefit depending on whether those years replace lower-earning years from earlier in your career.

If you have fewer than 35 years of earnings, Social Security includes zeros in your average. This is why workers who took time out for caregiving, unemployment, or other reasons often see lower benefits than workers with 35 full years of contributions. Each zero year pulls down your average, and you cannot remove it from the calculation.

Reductions That Lower Your Actual Payment

Your PIA is the starting point, but your actual monthly payment may be lower due to several reductions. The most common is the Government Pension Offset (GPO), which applies if you receive a pension from work where you did not pay Social Security taxes—typically federal, state, or local government employment. The GPO reduces your SSDI payment by two-thirds of your government pension amount. If your government pension is $900 per month, the GPO reduces your SSDI by $600.

A second reduction is the Windfall Elimination Provision (WEP), which also applies to people with government pensions. The WEP changes the bend point formula itself, making the first bend point replacement 40 percent instead of 90 percent. This can significantly lower your PIA if you have a government pension and also earned income subject to Social Security tax.

If you are under your full retirement age and earning income, Social Security reduces your benefit by $1 for every $2 you earn above the annual earnings limit. For 2024, that limit is $23,400. In the year you reach full retirement age, the reduction is $1 for every $3 earned above a higher limit ($62,160 in 2024), but only for earnings before the month you reach full retirement age. Once you reach full retirement age, no earnings reduction applies, regardless of how much you earn.

When Your Payment Changes Year to Year

Even if your circumstances do not change, your SSDI payment may increase each year. Social Security recalculates your PIA annually using updated bend points. The bend points rise each year based on the National Average Wage Index. This means your payment can go up even if you did not earn any new income, because the formula itself shifts.

Additionally, if you continue to work and earn income after you begin receiving SSDI, Social Security may recalculate your benefit using your new earnings. The agency automatically includes new earnings in your record and recalculates your 35-year average. If a new year of earnings replaces a zero year or a lower-earning year, your PIA increases. This recalculation happens automatically; you do not need to report new earnings for this purpose.

Social Security also applies a Cost of Living Adjustment (COLA) each year, usually in October. The COLA is a percentage increase applied to all benefit amounts to account for inflation. The percentage varies each year based on the Consumer Price Index. In years with high inflation, the COLA is larger; in years with low inflation, it is smaller or zero.

How to Review Your Earnings Record

You can request a detailed statement of your earnings record from Social Security to verify the years and amounts used in your PIA calculation. The easiest way is to create an account on ssa.gov and view your Social Security Statement online. The statement shows your reported earnings for each year since you began working, the years Social Security selected for your benefit calculation, and an estimate of your benefit amount.

If you see errors in your earnings record—missing years, incorrect amounts, or earnings attributed to the wrong year—you can file a correction request with Social Security. You will need documentation such as W-2 forms, tax returns, or a letter from your employer showing the correct earnings. Social Security has a three-year, three-month, and 15-day window from the end of the year the earnings were reported to correct errors, though some corrections can be made outside this window if you have strong evidence.

If you do not have online access or prefer to speak with someone, you can call Social Security at 1-800-772-1213 (TTY 1-800-325-0778) and request a paper Statement of Earnings. The agency will mail it to you within two weeks.

Why Two People With Similar Work Histories May Receive Different Amounts

Two workers with similar total lifetime earnings can receive different SSDI payments for several reasons. The timing of those earnings matters: someone who earned most of their income early in their career will have those earnings adjusted upward by the wage index, while someone who earned most of their income late in their career will have less wage adjustment. Someone who worked 40 years will have a higher average than someone who worked 35 years, because the 35-year average includes five zero years instead of five actual earnings years.

The age at which you became disabled also affects your calculation. Social Security uses your earnings up to the year you became disabled (or the year before, depending on when the disability began). If you became disabled at age 45, your calculation uses earnings only through age 44 or 45, whereas someone who worked until age 62 has 17 more years of potential earnings in their average.

Government pensions, ongoing work income, and other factors also create variation. Someone receiving a government pension will have their benefit reduced by the GPO or WEP, while someone without a government pension will not. Someone still working and under full retirement age will have their benefit reduced by the earnings test, while someone not working will receive their full PIA.

Frequently Asked Questions

Can I see the exact calculation Social Security used for my benefit?

Social Security does not provide a line-by-line breakdown of the bend point formula applied to your specific AIME, but your online Statement of Earnings shows your reported earnings by year and an estimate of your benefit. If you need more detail, you can request a detailed benefit calculation letter from your local Social Security office or by calling 1-800-772-1213.

What if I did not work for 35 years?

Social Security includes zero-earning years in your 35-year average. If you worked only 30 years, your average includes five years of zeros, which lowers your benefit. You cannot remove the zero years, but if you return to work and earn income, new earnings can replace the lowest-earning years in your record, potentially raising your benefit.

Does my SSDI payment go up if I get a raise at work?

If you are working and receiving SSDI, your benefit may increase when Social Security recalculates your record using your new earnings. However, if you are under full retirement age, your payment will be reduced by the earnings test ($1 reduction for every $2 earned above $23,400 in 2024). Once you reach full retirement age, you keep your full benefit regardless of work income.

Why did my payment amount change this year if I did not report anything new?

Social Security recalculates your PIA each year using updated bend points based on the National Average Wage Index. Additionally, the agency applies a Cost of Living Adjustment (COLA) to all benefits in October. Both of these changes can increase your payment without any action on your part.

How do I know if my earnings record has errors?

Review your Social Security Statement online at ssa.gov or request a paper statement by phone at 1-800-772-1213. Compare the reported earnings to your W-2 forms and tax returns for each year. If you find discrepancies, contact Social Security with copies of your W-2s or other documentation showing the correct amounts.