Your social security benefit is based on the 35 highest earning years in your work history. You can get your work history from the social security system (they may mail you a statement once a year or you can log into their system and download it.)
Suppose you worked continuously from age 18 to age 53, that's 35 years. If you take another job and earn more than your lowest year, the new earnings will replace the lowest year and will result in an increased benefit. If you made $5000 a year as a teen and can make $50,000 a year now, then each year you work will replace one of your bottom years and increase your benefit. On the other hand, if you take a small part-time job and the wages are less than the lowest year in your current history, that won't affect your benefit.
I don't have the formula to tell you exactly how much you can increase your benefit by working.
