Your account balance increases as you keep making deposits into it or as interest builds up over time. The amount of money in your account will determine how much interest you will receive. Typically, interest is determined as a percentage of your account balance. The amount of interest you earn rises along with your balance. If this growth is routinely compounded, it may become even more important. Consider keeping a healthy account level and taking advantage of accounts that offer tiered interest rates for bigger balances if you want to optimize your interest earnings.