The Calculator App
Compound Interest
Project a balance from a starting amount, contributions, and a rate you enter. This is not a forecast, an investment offer, or tax advice.
$300,850.72
Illustrative $10,000 starting balance, $500 monthly contribution, 7% rate, and 20 years of monthly compounding. Interest earned $170,850.72. Effective annual rate 7.23%. Not a quote. The interactive calculator replaces this summary in the browser.
How this growth estimate is built
You enter a starting balance, a contribution, a rate, and a number of years. Interest is posted at the compounding frequency you select. The periodic rate is that annual percent divided by the number of periods in a year. Nothing on this page looks up a rate or opens an account.
Questions
What is the ending balance?
It is the starting balance, plus every contribution, plus the interest posted on this schedule. The rate is the annual percent you enter. The calculator does not look up a savings yield or a market return.
When is the contribution added?
The default adds a contribution after interest when it lands on a posting date. More options can add it before interest instead. A contribution that arrives between posting dates does not earn interest until the next one. Daily compounding adds a monthly contribution on one day of each month, and interest posts every day after that. If you raise the growth percent, the contribution increases at the start of each later year.
Why do the compounding choices differ?
Annual, quarterly, monthly, and daily compounding split the same annual rate into 1, 4, 12, or 365 periods. More frequent posting applies interest to interest sooner. Daily compounding uses a 365-day year and does not add a leap day. The tiles keep the deposits and the rate the same so the gap is only the posting schedule.
What does this leave out?
Taxes, account fees, inflation, and a change in an investment price are not calculated. A higher rate raises the balance in this model. It does not mean an account will pay that rate.