Social Security uses your highest 35 years of earnings to calculate your SSDI benefit amount

The Social Security Administration does not use all the years you have worked. Instead, it takes your highest 35 years of earnings, adjusts them for inflation to today's dollars, and averages them to reach a number called your Primary Insurance Amount (PIA). This is the monthly payment you receive. If you have worked fewer than 35 years, Social Security counts the missing years as zero, which lowers your average and your benefit.

The calculation happens the same way whether you are on SSDI or have reached full retirement age and switched to Social Security retirement benefits. The difference is when you can start collecting—SSDI has no age requirement if you meet the medical criteria—but the math behind the payment is identical. Your benefit is locked in at the moment you become disabled, based on your earnings record up to that point.

Key Takeaways

  • Social Security counts your 35 highest-earning years; years below that count as zero, which reduces your average benefit.
  • Years are adjusted for inflation using a national wage index, so earnings from 1990 are not compared directly to earnings from 2020.
  • If you worked fewer than 35 years, the missing years as zeros lower your benefit amount permanently.
  • Your benefit is calculated once you are approved for SSDI and does not change based on future earnings unless you return to work above the substantial gainful activity threshold.
  • Self-employed income, military service credits, and railroad employment all count toward your 35-year record if reported to Social Security.

Why 35 years and not your whole work history

Social Security chose 35 years as the standard because it assumes most workers will have some years of low or no earnings—years spent in school, raising children, recovering from illness, or between jobs. By dropping the lowest years and counting only the highest 35, the formula gives you credit for a full career without penalizing you for gaps that are common in most people's lives.

If you have worked 40 years, Social Security drops your 5 lowest-earning years. If you have worked 30 years, it counts those 30 and adds 5 zeros. The zeros are permanent; you cannot erase them by working more after you are approved for SSDI. However, if you are still working and earning above the substantial gainful activity (SGA) limit—which is $1,550 per month in 2024, though this amount changes yearly—Social Security may suspend your benefits during those work months, and your benefit will not recalculate upward based on those new earnings.

How earnings are adjusted for inflation

A dollar you earned in 1995 is not worth the same as a dollar in 2024. Social Security adjusts for this using the National Average Wage Index, a figure published by the Social Security Administration each year. Your actual earnings from each year are multiplied by a factor that brings them to the wage level of the year you turn 60 (or the year you become disabled, if that is earlier). This is called wage indexing.

Wage indexing means your early career earnings are not ignored just because they were small in dollar terms. A job paying $15,000 in 1985 might be indexed to the equivalent of $50,000 in today's wages for the purpose of calculating your benefit. The Social Security Administration publishes the indexing factors each year on its website, and you can see the indexed amounts on your Social Security Statement if you create an account at ssa.gov.

What happens if you have not worked 35 years

Many people have not worked a full 35 years by the time they become disabled. This is common for people who became disabled in their 40s, or who spent years as a homemaker, student, or caregiver. If you have worked 28 years, Social Security counts those 28 years and adds 7 zeros to reach the 35-year total. Each zero reduces your average, and therefore your monthly benefit.

There is no way to remove those zeros after you are approved for SSDI. Working more years after approval does not recalculate your benefit upward. However, if you return to work and earn above the SGA threshold, your benefits will be suspended during those months, and when you stop working or drop below SGA, your original benefit resumes. The benefit itself does not change.

How your benefit changes if you return to work

If you are approved for SSDI and then return to work, your benefit does not automatically recalculate. Social Security has a trial work period that allows you to test your ability to work without losing benefits. During the trial work period—nine months in a rolling 60-month window—you can earn any amount and keep your full SSDI payment. After the trial work period ends, if you earn $1,550 or more per month (the 2024 SGA threshold), your benefits are suspended for that month.

If you work for several years above SGA and then stop, your benefit does not go up. It returns to the original amount it was before you started working. The only exception is if you become may be able to access for a different benefit—for example, if you reach full retirement age while on SSDI, your benefit may convert to a retirement benefit, which is calculated differently. For most people on SSDI, the benefit amount is set when approved and remains the same unless there is a cost-of-living adjustment (COLA), which happens once per year.

Special cases: military service, railroad work, and self-employment

If you served in the military before 1968, Social Security adds $300 per year of active service to your earnings record, even if you did not report earnings that year. This is called military wage credit and can help if you have gaps in your work history. Military service after 1967 is reported on your W-2 or tax return and counts as regular earnings.

If you worked for a railroad, your earnings may be covered under the Railroad Retirement Act instead of Social Security. Railroad employees and their families have a separate benefit system, though the calculation is similar. If you have both railroad and Social Security earnings, the two systems coordinate to avoid overpayment.

Self-employed income counts toward your 35-year record if you reported it on your tax return and paid self-employment tax. Unreported cash income does not count, even if you can prove you earned it. This is why keeping tax records is important for self-employed people who may later need to show their work history to Social Security.

How to see your own earnings record

You can view your Social Security earnings record by creating an account at ssa.gov and accessing your Social Security Statement. The statement shows your actual earnings for each year you worked, the years Social Security has on record, and an estimate of your future benefits. If you see errors—a year missing, an amount that is wrong, or a name change not reflected—you can request a correction by contacting Social Security directly.

Corrections must usually be made within three years, three months, and 15 days of the year the earnings were reported. If you are past that window, you may still be able to correct the record if you have a tax return or W-2 from that year. This is another reason to keep old tax documents: they are the proof Social Security uses to verify your earnings history.

Frequently Asked Questions

If I worked 40 years, which 5 years does Social Security drop?

Social Security automatically drops your 5 lowest-earning years, regardless of when they occurred. You do not choose which years are dropped. The system calculates your average using only the 35 highest years, so years with very low or zero earnings are excluded first.

Can I ask Social Security to use a different number of years?

No. The 35-year rule is set by federal law and applies to everyone. There is no option to use 30 years or 40 years instead. The only exception is for people born before 1929, who have different rules, but this applies to very few people today.

Does my SSDI benefit go up if I work part-time while disabled?

Not unless you earn above the SGA threshold and your benefits are suspended. If you work below SGA, your benefit stays the same. If you work above SGA, your benefit is suspended that month but does not increase when you return to work or stop working. The benefit amount is set when you are approved.

What if I have a gap of 10 years with no earnings?

Those 10 years count as zeros in your 35-year calculation, which lowers your average and your monthly benefit. You cannot remove them after approval. However, if you have worked 25 years, those 25 years plus 10 zeros still give you a benefit based on your 25 highest years averaged across 35 total years.

Does my spouse's earnings affect my SSDI benefit calculation?

No. Your SSDI benefit is based only on your own earnings record. Your spouse may be able to receive a benefit based on your record, but their earnings do not change your benefit amount. Spousal benefits are calculated separately and are typically 50 percent of your Primary Insurance Amount.