Over 40 percent of older Americans rely on Social Security for at least half of their retirement income; yet millions leave substantial money on the table simply because they misunderstand how the government calculates their benefits. Making decisions based on assumptions or outdated information can cost you tens of thousands of dollars over the course of your retirement. Because you have paid into this system throughout your working life, optimizing your claiming strategy is one of the most important financial moves you will make.

The calculation behind your monthly benefit is not a simple flat rate. It is a highly personalized formula driven by decades of your financial history, your marital status, and the precise timing of your retirement. Understanding the mechanics of this system allows you to take control of your income strategy and maximize the return on your lifelong contributions. Let us examine the eight primary factors that determine the exact dollar amount of your Social Security check.

Factor 1: Your Lifetime Earnings Record (The Top 35 Years)

The foundation of your Social Security benefit rests entirely on your lifetime earnings record. The Social Security Administration tracks your taxable wages throughout your entire career and uses a specific formula called the Average Indexed Monthly Earnings to determine your base benefit. When you apply for benefits, the agency adjusts your past earnings for inflation so that a salary earned in 1990 is valued in today’s wage environment.

Crucially, the government selects the 35 highest-earning years of your career to calculate this average. If you have worked for exactly 35 years, every single year counts. If you have worked for 42 years, the agency drops your seven lowest-earning years from the calculation, which naturally boosts your average. Conversely, if you have only worked for 28 years, you will have seven years of zeros factored into your average. These zero-earning years—often a result of staying home to raise children, dealing with extended unemployment, or taking early retirement—severely drag down your overall average and permanently reduce your monthly check.

You should proactively monitor your earnings record. Errors occur more frequently than people realize, often due to a name change, a clerical mistake by an employer, or a simple data entry error. Reviewing your annual statement directly through the Social Security Administration allows you to catch and correct missing wages before you file for benefits.