Compound Interest Calculator
See how a one-time deposit grows with compound interest. Enter the amount, rate, years, and how often interest compounds.
How to use it
Enter your initial deposit, the annual interest rate, the number of years, and how often interest compounds — annually, quarterly, monthly, or daily. The final balance and the total interest earned update as you type, so you can compare scenarios instantly. Everything is calculated in your browser, so none of your numbers are uploaded. Compound interest works by adding each period's interest back to the balance, so the next period earns interest on that interest as well as on the original deposit. That is why the balance curves upward instead of rising in a straight line: the growth feeds on itself. The calculation multiplies your principal by one plus the rate divided by the number of periods, raised to the power of the periods times the years. The compounding frequency sets how often interest is credited. Interest that compounds monthly is added twelve times a year rather than once, so it earns slightly more than the same rate compounded annually, and daily compounding edges ahead again. This tool models a single lump sum left to grow; if you plan to add money every month, the SIP calculator handles regular contributions instead. As a worked example, 10,000 invested at a 5 percent annual rate for 10 years grows to about 16,470 with monthly compounding, roughly 6,470 of which is interest. The same deposit compounded once a year reaches about 16,289, so more frequent compounding adds a modest extra amount, and the gap widens over longer horizons because there is more time for the interest-on-interest effect to build. Estimating compound growth this way is useful for projecting how savings or an investment might grow, comparing accounts with different rates or compounding schedules, and understanding the long-term power of leaving money invested. It is an estimate for illustration, not financial advice, and the whole calculation stays private on your device.
Frequently asked questions
- What does compounding frequency change?
- More frequent compounding (e.g. monthly vs annually) earns slightly more, because interest is added to the balance more often and then itself earns interest.
- Does this include regular contributions?
- No — this models a single lump-sum deposit. For recurring monthly contributions, use the SIP calculator; for paying down a loan, see the loan calculator.
- Is my data sent anywhere?
- No. The calculation runs entirely in your browser; nothing is uploaded.
- Why does compound interest grow faster over time?
- Each period's interest is added to the balance, so later periods earn interest on a larger and larger amount. Early on the effect is small, but because the growth compounds on itself the balance rises faster the longer the money is left invested, which is why time is the biggest factor in compound growth.