Most people check their Social Security statement and see a number, then move on. Few stop to ask where that number actually comes from. It turns out the formula is more logical than it looks, and once you understand it, your statement starts to tell a much clearer story about what you've built over your working years.
It Starts With Your 35 Highest-Earning Years
Social Security doesn't average every year you worked. It takes your 35 highest-earning years, adjusts each of them for inflation, and builds your benefit from that foundation.
The official term for those adjusted earnings is your AIME, or Average Indexed Monthly Earnings. The Social Security Administration (SSA) takes your top 35 years of earnings, adjusts them to reflect wage growth over your lifetime, adds them up, and divides by 420 (which is 35 years times 12 months). That result is your AIME.
If you worked fewer than 35 years, the SSA fills in the missing years with zeros. Those zeros pull your average down. For someone with a 30-year career, five zeroes enter the calculation, and that gap has a real effect on the monthly benefit they'll receive.
The Bend Point Formula
Your AIME doesn't translate dollar-for-dollar into a benefit. Instead, the SSA applies what's called a "bend point" formula, which is designed to replace a higher percentage of income for lower earners than for higher earners.
Here's how it worked for 2025:
The amount between $1,226 and $7,391 is replaced at 32%.
Anything above $7,391 is replaced at 15%.
The result of that calculation is called your PIA, or Primary Insurance Amount. That's the monthly benefit you'd receive if you claim at your full retirement age, which is 67 for anyone born in 1960 or later.
An example helps make this concrete. Suppose your AIME works out to $4,000 a month. The first $1,226 generates $1,103 in benefit (90%). The remaining $2,774 generates $888 (32%). Add those together and your PIA is roughly $1,991 a month. Your actual benefit at full retirement age would be close to that figure.
Why Timing Changes Everything
Your PIA is the baseline, but it's not necessarily what you'll receive. Claiming age shifts the number in both directions.
Claim at 62, the earliest possible age, and your benefit is reduced by up to 30% compared to what you'd get at 67. Claim at 70, the latest age that earns additional credits, and your benefit increases by 24% above your PIA. That's roughly a 54% difference between the lowest and highest monthly amounts, based on the same underlying earnings record.
There's no universally right answer on when to claim. It comes down to your health, whether you're still working, what other income you have, and what your spouse's situation looks like. But the math on the timing decision is one worth running carefully.
How to Check Your Own Numbers
The SSA provides a free online account atssa.gov/myaccountwhere you can see your full earnings history and your projected benefit at 62, your full retirement age, and 70. It's worth logging in even if retirement feels far away, because mistakes in your earnings record are real, and they're your responsibility to catch.
Look at each year of earnings and make sure it matches your own records. If a year is missing or lower than it should be, the SSA has a correction process, and catching errors early is far easier than correcting them after you've already filed.
The SSA also publishes a free guide on how benefits are calculated, available atssa.gov/pubs/EN-05-10070.pdf. It covers the bend point formula in plain terms with current figures.
A Few Things Worth Knowing
Working longer can help, even if you're already past 35 years. The formula always uses your highest 35, so a higher-earning year later in your career can replace a lower-earning year from early on. If you're in your 60s and still working, those years may be doing meaningful work on your benefit.
Spousal benefits follow a different path. A spouse who didn't work, or who earned significantly less, may be eligible for up to 50% of their partner's PIA. That's a separate calculation and doesn't reduce the worker's own benefit.
COLA adjustments happen after you claim. Once you're receiving benefits, the SSA adjusts them each year for inflation through what's called a COLA, or Cost-of-Living Adjustment. The 2025 COLA was 2.5%. These adjustments are applied to whatever monthly amount you locked in when you filed, which is another reason the claiming-age decision carries long-term weight.
Medicare premiums are often deducted directly. For most people on Medicare, Part B premiums come out of the Social Security check automatically. In 2025, the standard Part B premium was $185 a month. If you're planning around a specific net number, this deduction matters.
The Number on Your Statement Is a Starting Point
Your Social Security statement shows projected benefits, not guaranteed ones. Those projections assume you continue earning at your current level until you claim. If you plan to retire early, work part-time, or step back in your final years, your actual benefit will likely be lower than the projected figure.
The most accurate estimate comes from running your own numbers using the SSA's online tools or a Social Security calculator. The SSA's official Retirement Estimator is available atssa.gov/benefits/retirement/estimator.htmland lets you model different claiming ages and earning scenarios.
Understanding the formula won't make the decision for you. But it gives you something real to work with, rather than a number that arrives in the mail and has to be taken on faith.
This is educational information, not professional advice. Retirement rules change — Social Security, Medicare, and tax law are all subject to updates. Always verify current information with official government sources or a qualified professional before making decisions.