Compound Interest Calculator
Compound interest means you earn interest on your interest. Each month the balance grows, and the next month's interest is calculated on the larger balance. Over many years this effect becomes much bigger than the contributions themselves.
Compound Interest Calculator
Example values are shown to start with. Change them to your own numbers. Everything is calculated in your browser.
This calculator combines a starting balance with regular monthly contributions. It shows the future value, the total you contributed and the interest earned. It is useful for savings goals, for comparing rates, and for seeing how much starting early matters.
Worked example
With the starting values below, the calculator gives the results in the second table.
| Starting balance | ₹10,000 |
|---|---|
| Monthly contribution | ₹500 |
| Annual return | 8% |
| Years | 15 yrs |
| Future value | ₹2,06,088.33 |
|---|---|
| Total contributed | ₹1,00,000.00 |
| Interest earned | ₹1,06,088.33 |
How to use this calculator
- Enter the starting balance. It can be zero.
- Enter the amount you will add every month.
- Enter the expected annual return and the number of years.
- Read the future value, total contributed and interest earned.
Formula
- P is the starting balance.
- M is the monthly contribution, added at the end of each month.
- i is the monthly rate: annual return ÷ 12 ÷ 100.
- n is the number of months: years × 12.
Assumptions
- The rate is constant and compounds monthly.
- Contributions are made at the end of each month.
- Taxes, fees and inflation are not included.
Limitations
- Real savings and investment returns change over time.
- Inflation reduces what the future amount can buy.
Frequently asked questions
What is the compound interest formula with monthly contributions?
Future value = P × (1 + i)ⁿ + M × [((1 + i)ⁿ − 1) ÷ i], where P is the starting balance, M the monthly contribution, i the monthly rate and n the number of months.
Why does starting early matter so much?
Because interest compounds, money that is invested earlier has more time to grow, and the later years add the most. Try the same plan with a start ten years later to see the gap.
What rate should I use?
Use a rate that matches the account or investment, and try a lower one as well. For a savings account, use the stated rate.
Does the calculator include inflation?
No. To think in today's money, compare the result with how prices might rise over the same years.
Related calculators
- SIP CalculatorEstimate the maturity value of a monthly SIP investment.
- Lumpsum CalculatorGrowth of a one-time investment at a steady yearly return.
- CAGR CalculatorCompound annual growth rate between a starting and ending value.
Sources and method
This is the standard future value of savings with monthly compounding. See how our calculators work.
Results are estimates for planning only and are not financial, tax or legal advice. Rates, rules and your own circumstances can change the outcome. Read our disclaimer.