Benefit Calculation
Understanding the Calculation of SSDI Benefits
Verified against SSA POMS as of September 22, 2026
The short answer
Social Security Disability Insurance (SSDI) benefits are based on the worker's covered earnings history before becoming disabled. Social Security uses the worker's earnings to calculate an Average Indexed Monthly Earnings (AIME) amount and then applies the Social Security benefit formula to determine the worker's Primary Insurance Amount (PIA).
How SSDI Benefits Are Calculated
Unlike Social Security retirement benefits, which generally use the worker's highest 35 years of earnings, SSDI may use fewer years because a worker can become disabled before reaching retirement age.
Social Security determines the number of years to use based on the worker's age when the disability began. SSA then uses the applicable earnings history to calculate the worker's Average Indexed Monthly Earnings (AIME) and applies the Social Security benefit formula to determine the Primary Insurance Amount (PIA).
RS 00605.016RS 00605.017RS 00605.021Number of Earnings Years Used
The number of earnings years used in an SSDI calculation depends on the worker's age when the disability began. Social Security generally determines the number of elapsed years between age 22 and the year disability began and then allows certain low or zero-earning years to be dropped from the calculation.
Under the standard disability calculation, SSA generally allows one dropout year for every five elapsed years, up to five dropout years. At least two computation years are generally used.
RS 00605.230Disability Freeze
A disability freeze can exclude a period of disability from certain Social Security benefit calculations. This helps prevent years with little or no earnings because of a disability from lowering the worker's future Social Security benefits.
DI 25501.240RS 00605.220Other Public Disability Benefits
Workers' compensation and certain other public disability benefits may reduce the amount of SSDI payable.
When the offset applies, the combined amount of SSDI and the other public disability benefit is generally limited to 80% of the worker's average current earnings before disability, subject to specific exceptions and calculation rules.
20 CFR 404.408 View source ›Frequently asked
Does SSDI use the same 35-year earnings calculation as Social Security retirement benefits?
Although SSDI and retirement benefits both use an AIME and PIA calculation, SSDI may use fewer years of earnings because the worker may become disabled before retirement age. The number of years used depends on the worker's age when the disability began.
Does the severity of my disability determine the amount of my SSDI benefit?
No. The amount of SSDI is based on the worker's covered earnings history, not the severity of the disability. Once the worker meets Social Security's definition of disability, having a more severe disability does not result in a higher SSDI benefit.
Do other sources of income reduce my SSDI benefit?
Generally, no. SSDI is not means-tested, so income such as pensions, retirement account withdrawals, investment income, or a spouse's earnings does not reduce the SSDI benefit. However, the beneficiary's own work activity and earnings can affect SSDI, and workers' compensation or certain other public disability benefits may reduce the amount payable.
What happens to my SSDI when I reach full retirement age?
SSDI automatically converts to Social Security retirement benefits when the beneficiary reaches full retirement age. The benefit is no longer paid as a disability benefit but instead becomes a retirement benefit.