How are FERS disability benefits computed?
If at disability retirement you are already 62 years old, or you meet the age and service requirements for immediate unreduced, voluntary retirement, your benefit will be calculated under the standard FERS formula.

If at disability retirement you are under age 62 and not eligible for voluntary retirement:
• for the first 12 months you will receive 60 percent of your high-3 average salary minus any Social Security disability benefits;
• afterward, you will receive 40 percent of your high-3 average salary minus 60 percent of any Social Security disability benefits.

However, you are entitled to your earned annuity—1 percent of your high-3 average salary multiplied by your years and months of service—if it is larger than your disability annuity computed under either of those formulas. Once you reach age 62, the benefit is recomputed as if you had worked to that age, using your high-3 at the onset of your disability increased by the FERS cost-of-living increases in the interim.