How Your SSDI Benefit Amount Is Calculated
TL;DR: Your SSDI payment is calculated using three steps: (1) Index your earnings for inflation and select the highest 35 years, (2) Calculate your Average Indexed Monthly Earnings (AIME), (3) Apply the PIA formula with bend points (90% of first $1,174, 32% of $1,174-$7,078, 15% above $7,078 in 2026). The result is your Primary Insurance Amount (PIA), your monthly benefit. Higher lifetime earnings = higher payment. You can check your estimated benefit at ssa.gov/myaccount.
SSDI is not a flat-rate benefit. Your payment is a personalized calculation based on your lifetime earnings. Understanding the formula helps you know what to expect and whether your Social Security Statement estimate is accurate.
Step 1: Index Your Earnings
The SSA takes your yearly earnings and adjusts (indexes) them for wage inflation. This makes earnings from 20 years ago comparable to recent earnings in today's dollars.
Step 2: Calculate AIME
The SSA selects your highest 35 years of indexed earnings, adds them up, and divides by 420 (35 years x 12 months). The result is your Average Indexed Monthly Earnings. Years with zero or low earnings pull your average down.
Step 3: Apply the PIA Formula
The 2026 bend points determine how much of your AIME converts to benefits:
| AIME Range | Replacement Rate |
|---|---|
| First $1,174 | 90% |
| $1,174 to $7,078 | 32% |
| Above $7,078 | 15% |
Example
AIME of $4,000:
- 90% of $1,174 = $1,056.60
- 32% of ($4,000 - $1,174) = $904.32
- PIA = $1,960.92/month
The formula is progressive: lower earners get a higher percentage replaced, but higher earners get a higher dollar amount.
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Frequently Asked Questions
How Your SSDI Benefit Amount Is Calculated?
TL;DR: Your SSDI payment is calculated using three steps: (1) Index your earnings for inflation and select the highest 35 years, (2) Calculate your Average Indexed Monthly Earnings (AIME), (3) Apply the PIA formula with bend points (90% of first $1,174, 32% of $1,174-$7,078, 15% above $7,078 in 2026). The result is your Primary Insurance Amount (PIA), your monthly benefit. Higher lifetime earnings = higher payment.
What is the process for step 1: index your earnings?
The SSA takes your yearly earnings and adjusts (indexes) them for wage inflation. This makes earnings from 20 years ago comparable to recent earnings in today's dollars.
What is the process for step 2: calculate aime?
The SSA selects your highest 35 years of indexed earnings, adds them up, and divides by 420 (35 years x 12 months). The result is your Average Indexed Monthly Earnings. Years with zero or low earnings pull your average down.
What is the process for step 3: apply the pia formula?
The 2026 bend points determine how much of your AIME converts to benefits: