Compound Interest Calculator with Monthly Deposits
See how savings grow with compound interest. Enter a starting amount, rate, years, compounding frequency and regular deposits to get the final balance, total interest and a year-by-year table.
Deposits are added at the end of each month or year.
- Final balance
- 31,998.32
- Total deposits
- 22,000.00
- Total interest
- 9,998.32
- Effective annual rate
- 5.12%
Year by year
| Year | Deposits | Interest | End balance |
|---|---|---|---|
| 1 | 1,200.00 | 539.50 | 11,739.50 |
| 2 | 1,200.00 | 628.50 | 13,568.01 |
| 3 | 1,200.00 | 722.05 | 15,490.06 |
| 4 | 1,200.00 | 820.39 | 17,510.44 |
| 5 | 1,200.00 | 923.75 | 19,634.20 |
| 6 | 1,200.00 | 1,032.41 | 21,866.60 |
| 7 | 1,200.00 | 1,146.62 | 24,213.23 |
| 8 | 1,200.00 | 1,266.68 | 26,679.91 |
| 9 | 1,200.00 | 1,392.88 | 29,272.79 |
| 10 | 1,200.00 | 1,525.54 | 31,998.32 |
About the Compound Interest Calculator
The Compound Interest Calculator shows how a lump sum and regular savings grow when interest is paid on interest. Enter a starting amount, an annual interest rate, the number of years and how often the interest compounds. Add an optional monthly or yearly deposit to see the effect of saving a fixed amount every period. The calculator returns the final balance, the total you paid in, the total interest earned and the effective annual rate, followed by a year-by-year table of deposits, interest and end balance.
It works with any currency: amounts are shown with two decimals and no currency symbol. The result is an estimate at a fixed rate before tax, fees and inflation, and it is not financial advice.
How to use it
Steps
- Type the Initial amount you start with. Zero is fine if you only make deposits.
- Enter the Annual interest rate in percent, for example 5 for 5 percent, and the number of Years from 1 to 100.
- Pick how often the interest compounds: annually, semiannually, quarterly, monthly or daily.
- Optionally add a Regular deposit and choose whether it is made monthly or yearly.
- Read the results as you type, then scroll the yearly table to see how the balance builds up.
Deposits and compounding
Deposits are added at the end of each month or year. When the deposit schedule differs from the compounding schedule, for example monthly deposits into an account that compounds yearly, the nominal rate is converted to the exactly equivalent rate per deposit period, so every deposit earns the correct amount of interest.
The formulas
A starting amount at a nominal annual rate , compounded times a year for years, grows to
A deposit made at the end of each of periods a year earns the equivalent periodic rate , and the deposits grow to the future value of an annuity:
When the rate is zero the deposits simply add up, . The effective annual rate is .
Worked examples
- Lump sum: 10,000 at 5 percent compounded annually for 10 years grows to 16,288.95, so 6,288.95 is interest.
- Monthly compounding: 1,000 at 6 percent compounded monthly for one year grows to 1,061.68. The effective annual rate is 6.17 percent, slightly above the nominal 6 percent.
- Monthly saving: 100 deposited at the end of every month for 10 years at 6 percent compounded monthly grows to 16,387.93 from 12,000 paid in.
The rule of 72
For a quick estimate of how long money takes to double, divide 72 by the rate in percent. At 6 percent money doubles in roughly 12 years, and at 9 percent in roughly 8 years. The rule is an approximation that works best between about 4 and 12 percent; the calculator gives the exact balance for any rate.
Privacy
Nothing is uploaded; every calculation runs in your browser and never leaves your device.
Related tools
Borrowing rather than saving? The Loan Calculator shows repayments and total interest on a loan. To see what a future amount is worth in today's money, use the USD Inflation Calculator, and the Percentage Calculator handles quick percentage changes.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Each period the interest is added to the balance, so the next period's interest is a little larger. Over many years this snowball effect makes savings grow much faster than simple interest.
How often should interest compound?
More frequent compounding earns slightly more at the same nominal rate. At 6 percent a year, annual compounding gives an effective rate of 6.00 percent, monthly gives 6.17 percent and daily gives about 6.18 percent. Use the frequency your bank or fund states, often shown as the APY or AER.
What is the effective annual rate shown in the results?
It is the annual percentage yield (APY): the growth you get in one year once compounding is included, calculated as (1 + r/n)^n − 1. It lets you compare accounts that compound at different frequencies on equal terms.
When are regular deposits added?
At the end of each month or year, which is how most savings plans and the standard future-value formula work. If your deposits compound on a different schedule from the interest, the calculator converts the nominal rate to the exactly equivalent rate per deposit period, so the result stays accurate.
Does the calculator include tax, fees or inflation?
No. It shows growth at a fixed rate before tax, fees and inflation. To see what a future amount is worth in today's money, try the USD Inflation Calculator. Real returns vary, so treat the result as an estimate rather than financial advice.
What is the rule of 72?
It is a quick way to estimate how long money takes to double: divide 72 by the annual interest rate in percent. At 6 percent money doubles in about 12 years, and at 8 percent in about 9 years. The calculator gives the exact figure for any rate.