How Your Social Security Retirement
Benefit is Determined

Author: James Kranig
Last Update : 05/20/2026


Overview

Your Social Security retirement benefit is not a guess, a rule of thumb, or a negotiation. It is the result of a precise formula, as specified by Federal law, that blends your lifetime earnings, the age you start benefits, and adjustments for inflation. Understanding the mechanics of benefit calculation is an important part of understanding the best time to start your benefits.

This article walks through the key components that determine your benefit and shows how they interact to shape your monthly payment.


Your Lifetime Earnings Record: The Foundation of Your Benefit

Your earnings record is the single most important factor in determining your Social Security retirement benefit.

SSA uses your highest 35 years of inflation-adjusted earnings

When you apply for benefits, the Social Security Administration reviews every year in which you paid Social Security payroll taxes and selects your 35 highest-earning years, adjusted for national wage inflation. These “indexed earnings” reflect what your past earnings would be worth in today’s wage environment.

Key Earnings Indexing Rules:

  • Indexing uses the National Average Wage Index (AWI) as of two years prior.
  • Earnings are indexed only through age 60. Earnings at 61 and later are included at face value.
  • If you have fewer than 35 years of earnings, SSA fills the missing years with zeros, which lowers your benefit.

Indexed Earnings Example: Betty is now (2026) 62 and earned $18,000 in 1986. The wage index factor (growth in the average wage index) from 1986 to 2024 is 4.0322882. Therefore, as of 2026, Betty's 1986 indexed earnings are:

$18,000 x 4.0322882 = $72,581.19

Average Indexed Monthly Earnings (AIME)

Once your earnings have been indexed for inflation, the Social Security Administration sums your highest 35 years of indexed earnings and divides this amount by 420 months (35 years × 12 months per year) to produce your AIME.

AIME Example: The sum of Betty's highest 35 years of inflation indexed earnings is $2,100,000. Therefore her AIME is:

$2,100,000 / 420 months = $5,000 per month.

Primary Insurance Amount (PIA): The Core Benefit Formula

Once your AIME is determined, it is used in a formula to calculate your Primary Insurance Amount (PIA) which is the benefit you would receive if you retire at your Full Retirement Age (FRA) - 67 for those born in 1960 or later and between 66 and 66 and 10 months for those born earlier.

The PIA formula uses the concept of “bend points” that are adjusted each year for inflation. Instead of using a single percentage of AIME to determine benefits for all recipients, bend points are used to ensure lower-income workers get a higher percentage of their wages replaced in retirement. The PIA formula replaces:

  • 90% of the first portion (up to $1,174 in 2026) of AIME
  • 32% of the next portion above the first portion (up to $7,078 in 2026) of AIME
  • 15% of the remainder

While the 90%, 32%, and 15% percentages remain fixed, the portions (dollar thresholds) to which they apply are adjusted annually by the SSA to keep up with the national Average Wage Index (AWI). The PIA formula uses the bend points for the year the worker turns 62.

PIA Example: Betty's Average Indexed Monthly Earnings (AIME) are $5,000. Given the fixed bend point percentages and portions (thresholds) for 2026, her Primary Insurance Amount (PIA) is calculated as follows:

0.90 x ($1,174) + 0.32 x ($5,000 - $1,174) + 0.15 x ($0) = $2,158.49


The Age You Start Benefits: Reductions and Credits

You can start benefits anytime from age 62 to 70, but the age you choose can reduce/increase your benefit below/above your Primary Insurance Amount.

Starting benefits before Full Retirement Age

If you claim benefits prior to your Full Retirement Age (FRA), your benefit is permanently reduced by a percentage for the months between your actual benefit start month and the month you reach your FRA. The monthly percentage reductions are:

  • 0.5556% for each month from the month you turn 62 to the month you turn 65.
  • 0.4167% for each month after you turn 65 up to the month you reach your FRA.

Early Benefit Start Example: Betty decides to start receiving Social Security retirement benefits at age 62. If her Primary Insurance Amount is $2,158.49, then her benefit would be:

$2,158.49 x (1 - 0.005556 x 36 - 0.004167 x 24) = $1,510.89*

*assuming a COLA of 0% in the year Betty turns 62.

Starting at Full Retirement Age

At Full Retirement Age (FRA), you receive 100% of your Primary Insurance Amount (PIA).

Full Retirement Age Benefit Start Example: Betty decides to start receiving Social Security retirement benefits at age 67 - her Full Retirement Age. If her Primary Insurance Amount is $2,158.49, then her benefit would also be $2,158.49*.

*assuming a COLA of 0% from the year Betty turns 62 to the year she turns 67.

Delaying past Full Retirement Age

If you delay benefits past your FRA, you start earning Delayed Retirement Credits of 8% per year (0.67% per month), up to age 70. These credits increase you monthly benefit above your FRA benefit. You will recieve no additional delay credits once you reach age 70.

Delayed Retirement Benefit Start Example: Betty decides to start receiving Social Security retirement benefits at age 70. If her Primary Insurance Amount is $2,158.49, then her benefit would be:

$2,158.49 x (1 + 0.006666667 x 36) = $2,676.53*

*assuming a COLA of 0% from the year Betty turns 62 to the year she turns 70.


Cost of Living Adjustments (COLAs)

Whichever month you do decide to claim your benefits, you will receive any yearly Social Security Cost of Living adjustments (COLA) from the year you turn 62 to the year you claim benefits. The COLA is applied to your Primary Insurance Amount before any reductions or credits are applied.

Once you start your benefits, you will continue to receive annual COLAs which will increase future benefits.

Benefit Start COLA Adjustment Example: Betty decides to start receiving Social Security retirement benefits at age 62. If her Primary Insurance Amount is $2,158.49 and the Social Security COLA for the year she turns 62 is 1%, then her benefit would be:

$2,158.49 x (1 + 0.01) x (1 - 0.005556 x 36 - 0.004167 x 24) = $1,526.00


Summary

Your Social Security retirement benefit is determined by:

  • Your highest 35 years of inflation-adjusted earnings
  • A progressive formula that produces your Primary Insurance Amount (PIA)
  • The age you start benefits, which permanently reduces or increases your monthly payment
  • COLAs applied from age 62 onward

These components interact in ways that can significantly affect your lifetime benefits - which is why understanding the calculation is essential when choosing your start age.

For an overview of the factors you should consider in deciding when to start benefits see our article on the key factors to consider.


Social Security Analytics - Retirement Benefit Estimation Tool

If you want to see estimates for your starting retirement benefit for every possible start month/age, Social Security Analytics provides a tool that does just that. Our Social Security Retirement Benefit Estimator uses the same formulas as the Social Security Administration. Unlike other benefit estimation tools, you can easily adjust inputs to perform what-if analyses, changing, for example, your future income growth percentage, Social Security COLA assumptions as well as factor in a future benefit cut. See our benefit estimation FAQs for more information.

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