How to Calculate Your Social Security Disability Benefit Amount

Your SSDI Benefit Equals Your Full Primary Insurance Amount

Social Security Disability Insurance (SSDI) pays your Primary Insurance Amount (PIA) in full. Unlike early retirement benefits, SSDI does not apply an age-based reduction. The SSA calculates your PIA using the same formula it uses for retirement benefits. That makes understanding the PIA formula the single most important step in projecting your monthly payment.

The PIA formula has three inputs: your covered earnings history, the Average Indexed Monthly Earnings (AIME), and the bend-point percentages the SSA applies to your AIME. Each step builds directly on the previous one.

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Step 1: Build Your Earnings History and Identify the Computation Years

The SSA indexes your past wages to account for wage growth over time. It then selects the highest 35 years of indexed earnings to compute your AIME. If you become disabled before accumulating 35 years of covered earnings, the SSA fills the remaining slots with zeros. Each zero year pulls the AIME down and reduces your monthly benefit.

For workers who become disabled at younger ages, the SSA uses a reduced number of computation years. The formula is: (years elapsed between age 21 and the year of disability onset) minus 2, with a floor of 2 years. A 32-year-old disabled worker might use only 9 computation years instead of 35, which limits the damage from sparse earnings history.

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Step 2: Calculate Your Average Indexed Monthly Earnings (AIME)

Your AIME equals the sum of your highest indexed annual earnings, divided by the number of months in your computation period.

Plain-text formula: AIME = (Sum of highest indexed annual earnings) / (Computation years x 12)

The SSA indexes each year's earnings by multiplying them by the ratio of the national average wage in the indexing year to the national average wage in the earnings year. Wages from recent years before disability onset are not indexed. They count at their nominal value.

Worked Example 1: Lower Earnings History

Maria, age 41, files for SSDI in 2025. Her 20 computation years (41 minus 21, minus 2, rounded to 20) of highest indexed earnings total $480,000. Her AIME equals $480,000 divided by 240 months, which equals $2,000 per month.

Worked Example 2: Mid-Career Earner

David, age 52, files for SSDI in 2025. His 29 computation years of highest indexed earnings total $1,044,000. His AIME equals $1,044,000 divided by 348 months, which equals $3,000 per month.

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Step 3: Apply the Bend-Point Formula to Get Your PIA

The SSA applies three percentages to three segments of your AIME. The dollar thresholds, called bend points, adjust annually. For 2025, the bend points are $1,226 and $7,391.

The formula works as follows:

• 90% of the first $1,226 of AIME
• 32% of AIME between $1,226 and $7,391
• 15% of AIME above $7,391

Sum the three results. Round down to the nearest $0.10. That is your PIA and your monthly SSDI payment before any deductions.

Worked Example 1 Continued: Maria's PIA

Maria's AIME is $2,000.

• 90% x $1,226 = $1,103.40
• 32% x ($2,000 - $1,226) = 32% x $774 = $247.68
• 15% x $0 = $0.00

Maria's PIA = $1,103.40 + $247.68 = $1,351.08. Her monthly SSDI benefit is $1,351.00 (rounded down to nearest $0.10).

Worked Example 2 Continued: David's PIA

David's AIME is $3,000.

• 90% x $1,226 = $1,103.40
• 32% x ($3,000 - $1,226) = 32% x $1,774 = $567.68
• 15% x $0 = $0.00

David's PIA = $1,103.40 + $567.68 = $1,671.08. His monthly SSDI benefit is $1,671.00.

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Three Factors That Reduce Your Net SSDI Payment

Medicare Part B Premiums

The SSA deducts Medicare Part B premiums from SSDI payments once a recipient enrolls in Medicare. The 2025 standard Part B premium is $185.00 per month. That reduces a $1,351 benefit to $1,166 in actual cash received.

Workers' Compensation and Public Disability Offsets

If you receive workers' compensation or a public disability benefit, the SSA may reduce your SSDI payment so that combined benefits do not exceed 80% of your pre-disability average current earnings. This offset can eliminate a significant portion of your monthly SSDI check.

Taxation of SSDI Benefits

Single filers with combined income above $25,000 pay federal income tax on up to 50% of their SSDI benefit. Above $34,000, up to 85% becomes taxable. Married filers face those thresholds at $32,000 and $44,000 respectively. State income tax treatment varies. Thirteen states tax Social Security benefits in some form.

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How to Get Your Actual Earnings Record

The SSA bases your SSDI calculation on the earnings posted to your Social Security record, not what you remember earning. Errors in that record directly reduce your benefit. Access your full earnings history through your my Social Security account at ssa.gov. Review every year. Dispute discrepancies using IRS W-2 forms or tax returns as documentation. The SSA corrects verified errors, and even a single corrected year can raise your AIME by $50 to $150 per month.

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Run Your Own SSDI Estimate Before You File

The SSA's bend-point formula rewards high-earning years disproportionately at lower income levels and plateaus quickly above the second bend point. Knowing exactly where your AIME falls relative to the $1,226 and $7,391 thresholds tells you how each additional dollar of past earnings affects your benefit.

The CalcMoney Retirement Calculator applies the 2025 bend-point formula to your inputs and returns a PIA estimate in seconds. Enter your AIME, select your computation period, and see exactly how your benefit breaks down across all three tiers. Use that number to verify the SSA's own estimate from your my Social Security account, or to model how different earnings scenarios shift your monthly payment before you file.

Run your SSDI benefit estimate with the CalcMoney Retirement Calculator →

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Results are estimates for informational purposes only. Consult a licensed financial professional before making financial decisions.