The Basic Formula: Primary Insurance Amount and Your Work History

Your monthly SSDI payment is based on your Primary Insurance Amount (PIA), which Social Security calculates from your lifetime earnings record. The calculation uses your 35 highest-earning years of work (after adjusting older earnings for inflation), drops out the lowest years, and averages what remains. That average becomes the basis for your PIA.

The Social Security Administration then applies a bend point formula to that average. This formula replaces a higher percentage of your first dollars of earnings and a lower percentage of your higher earnings — meaning lower-wage workers receive a larger percentage of their past earnings as a benefit. The exact bend points change each year and are published by Social Security in January.

Your PIA is the amount you would receive at your full retirement age. If you are approved for SSDI before that age, you receive the same PIA amount (unlike retirement benefits, which are reduced for early claiming). If you have dependents — a spouse, ex-spouse, or children under 19 (or 19 if still in high school) — they may receive their own payments based on your PIA, but the family maximum applies.

Key Takeaways

  • Your benefit amount comes from your Primary Insurance Amount, which is calculated using your 35 highest-earning years of work history adjusted for inflation.
  • The bend point formula gives you a higher replacement rate on lower earnings and a lower rate on higher earnings, so lower-wage workers see a larger percentage of past earnings as a benefit.
  • You can request a detailed earnings record and benefit estimate from Social Security before you file, using your my Social Security account or by calling 1-800-772-1213.
  • If you have a spouse, ex-spouse, or children under 19, they may receive payments based on your record, but the family maximum caps the total amount all family members can receive.
  • Working while on SSDI triggers the Substantial Gainful Activity (SGA) limit, which in 2024 is $1,550 per month; exceeding it can suspend your benefits that month.

How Social Security Adjusts Your Earnings for Inflation

Social Security does not use your actual dollar amounts from 30 years ago. Instead, it adjusts your earnings from each year up to age 60 using the National Average Wage Index. This index measures the average wage across the entire U.S. economy in each year.

Here is how it works: Social Security takes your actual earnings in, say, 1995, and multiplies them by the ratio of the National Average Wage Index for the year you turn 60 to the index for 1995. This brings your old earnings into current-dollar terms so they can be fairly compared to more recent earnings. Earnings after age 60 are not adjusted — they are used at their actual dollar value.

You can see the National Average Wage Index for past years on the Social Security website. This adjustment is why your benefit statement may show much larger "indexed" earnings than the actual paychecks you received decades ago.

Understanding the Bend Points and Replacement Rates

Once Social Security has your 35-year average indexed earnings (called your Average Indexed Monthly Earnings, or AIME), it applies the bend point formula. In 2024, the formula works like this: you receive 90 percent of your first $1,174 of AIME, then 32 percent of AIME between $1,174 and $7,078, then 15 percent of anything above $7,078.

These bend point dollar amounts change each year. They are tied to the National Average Wage Index and are announced in October for the following year. The percentages (90, 32, and 15 percent) never change — only the dollar thresholds move.

The effect is progressive: a worker whose AIME is $2,000 receives a much higher percentage of their past earnings than a worker whose AIME is $8,000. This is why SSDI replaces a larger share of income for lower-wage workers.

What Happens If You Have Work Credits or Gaps in Your Record

You must have earned at least 40 work credits to be insured for SSDI (you can earn up to four credits per year). If you have fewer than 40 credits, you are not insured, and Social Security will deny your claim regardless of your disability.

If you have gaps in your earnings record — years with no income or very low income — those years still count toward your 35-year average. Social Security uses your 35 highest-earning years and drops the rest. If you have worked fewer than 35 years, the missing years are counted as zeros, which lowers your average and your benefit amount.

You can request a detailed earnings record from Social Security to verify that all your work has been credited. Errors are not uncommon, especially if you changed your name, had multiple jobs in one year, or worked under a different Social Security number. Correcting errors before you file can increase your benefit.

Family Maximum and How It Affects Dependents

If you have a spouse, ex-spouse, or children under 19 (or 19 if in high school) on your record, each may receive a payment based on your PIA. A spouse or ex-spouse typically receives 50 percent of your PIA; each child receives 75 percent of your PIA.

However, the family maximum limits the total amount all family members can receive combined. The family maximum is usually between 150 and 180 percent of your PIA, depending on the bend point formula for your year of birth. If the sum of all family members' payments would exceed the maximum, Social Security reduces each dependent's payment proportionally.

For example, if your PIA is $1,500 and the family maximum is 175 percent ($2,625), and you have a spouse and two children, each would normally receive $750, $1,125, and $1,125 respectively — a total of $3,375. Since that exceeds $2,625, Social Security reduces each payment by the same percentage so the total equals the maximum.

How Work and Earnings Affect Your Monthly Benefit

If you work while receiving SSDI, your benefit is not automatically reduced dollar-for-dollar. Instead, Social Security uses the Substantial Gainful Activity (SGA) test. In 2024, SGA is $1,550 per month for non-blind workers and $2,590 for blind workers. If your monthly earnings stay below SGA, your benefits continue in full.

If you exceed SGA in a month, Social Security may suspend your benefits for that month. However, you have a trial work period of nine months (not necessarily consecutive) during which you can earn any amount without losing benefits. After the trial work period ends, you enter the extended may be able to access period, which lasts 36 months. During this period, you lose benefits only in months when you exceed SGA.

Self-employment income is also counted. Social Security looks at your net profit (revenue minus business expenses) and may count only a portion of your time spent on the business, depending on the circumstances. If you are self-employed, report your income carefully and discuss your situation with a work incentives planning specialist before you start or expand a business.

Using Your Social Security Statement to See Your Estimated Benefit

You can create a free my Social Security account at ssa.gov to view your earnings record and see an estimate of your SSDI benefit. The estimate is based on your current earnings record and assumes you become disabled at your current age. The estimate updates once per year.

If you do not have an online account, you can call Social Security at 1-800-772-1213 (TTY 1-800-325-0778) and request a printed statement. Response times vary, but you should receive it within two weeks. The statement shows your earnings year by year, your work credits, and an estimate of your SSDI, retirement, and survivor benefits.

Keep in mind that the estimate assumes you have no more earnings after the current year. If you continue to work and earn more, your benefit may increase slightly, because Social Security will use your new higher-earning years instead of lower-earning years from the past. However, the increase is usually modest unless you are still in your peak earning years.

Frequently Asked Questions

Can I see the exact calculation before I file for SSDI?

You can see an estimate through your my Social Security account or by requesting a statement by phone. The estimate shows your Primary Insurance Amount based on your current record. The exact calculation happens only after Social Security processes your claim, but the estimate is usually accurate within a few dollars.

What if I did not work for 35 years?

Social Security still uses 35 years in the calculation. If you worked only 20 years, the other 15 years count as zeros, which lowers your average and your benefit. This is why people who took time out of the workforce for caregiving, illness, or other reasons often receive lower SSDI payments than those with continuous work histories.

Does my SSDI benefit increase after I start receiving it?

Your benefit increases each year by the cost-of-living adjustment (COLA), which is announced in October and takes effect in January. COLA is tied to inflation and varies year to year. Your benefit does not increase based on new earnings once you are on SSDI, unless you return to work and then stop, at which point Social Security recalculates your PIA using your new earnings record.

How does a divorce affect my SSDI benefit?

Your own SSDI benefit does not change. However, an ex-spouse may be able to receive a payment on your record if the marriage lasted at least 10 years and they are at least 62 years old (or any age if caring for your child under 16). This does not reduce your benefit or your current spouse's benefit.

What if Social Security made an error in my earnings record?

Contact Social Security when ready with proof of the error — W-2s, tax returns, or pay stubs. Social Security can correct errors going back three years, three months, and 15 days from the date you report them. Older errors may be corrected if you have documentary evidence. Correcting errors before you file can significantly increase your benefit.