Compound Interest Calculator With Monthly Deposits
This compound interest calculator shows how money grows when interest earns interest. Enter a starting amount, a monthly deposit, a yearly rate and a number of years, and see the final balance, how much came from your deposits and how much from interest, with a year-by-year table.
| Year | Deposits | Interest | Balance |
|---|
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Quick answer: $10,000 plus $200 a month at 7% compounded monthly grows to about $144,000 after 20 years. You put in $58,000; the other $86,000 or so is interest.
How to use the compound interest calculator
- Enter your starting amount (use 0 if you are starting from nothing) and how much you will add each month.
- Enter the expected yearly interest rate or return and the number of years.
- Choose how often interest is compounded. Savings accounts often compound daily or monthly; many bonds and fixed deposits compound quarterly or yearly.
- Read the final balance and the table to see how the interest snowballs in later years.
The compound interest formula
For a single deposit: A = P (1 + r/n)nt, where P is the starting amount, r the yearly rate as a decimal, n the number of times interest is compounded per year and t the number of years. With monthly deposits, each deposit grows for the months that remain. This calculator adds deposits at the end of each month and converts the compounding to an equivalent monthly rate, which is how most banks quote it.
Simple vs compound interest
Simple interest is paid only on the original amount. Compound interest is paid on the amount plus all interest so far, so growth speeds up over time. $10,000 at 7% simple interest earns $14,000 in 20 years; compounded yearly it earns about $28,700.
The rule of 72
Divide 72 by the yearly rate to estimate how many years it takes to double your money. At 6% that is about 12 years; at 9%, about 8 years. The status line under the results shows the exact doubling time.
| Rate | Years to double |
|---|---|
| 3% | 23.4 |
| 5% | 14.2 |
| 7% | 10.2 |
| 10% | 7.3 |
| 12% | 6.1 |
Returns on stocks and funds go up and down, and this tool does not include taxes, fees or inflation. Treat the result as an estimate, not financial advice. To work out loan payments instead, use the loan calculator; to convert pay between hourly and yearly, use the salary calculator.
FAQ
What is APY?
Annual percentage yield is the real yearly growth after compounding. 5% compounded monthly is an APY of 5.12%.
Does daily compounding make a big difference?
Only a little over monthly compounding. The rate, the time and how much you add each month matter far more.
Can I use this for a SIP?
Yes. Set the starting amount to 0, enter your monthly SIP amount and an expected return.
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