Investing
Compound Interest Calculator
Enter a starting amount, a monthly contribution, an assumed annual return and a number of years to see the final balance, how much of it you paid in and how much came from compounding, year by year.
Compound interest calculator
- Final balance
- 300,850.72
- Total contributed
- 130,000
- Total growth
- 170,850.72
Show the year-by-year table
| Year | Contributed | Growth | Balance |
|---|---|---|---|
| 1 | 16,000 | 919 | 16,919 |
| 2 | 22,000 | 2,339 | 24,339 |
| 3 | 28,000 | 4,294 | 32,294 |
| 4 | 34,000 | 6,825 | 40,825 |
| 5 | 40,000 | 9,973 | 49,973 |
| 6 | 46,000 | 13,782 | 59,782 |
| 7 | 52,000 | 18,299 | 70,299 |
| 8 | 58,000 | 23,578 | 81,578 |
| 9 | 64,000 | 29,671 | 93,671 |
| 10 | 70,000 | 36,639 | 106,639 |
| 11 | 76,000 | 44,544 | 120,544 |
| 12 | 82,000 | 53,455 | 135,455 |
| 13 | 88,000 | 63,443 | 151,443 |
| 14 | 94,000 | 74,587 | 168,587 |
| 15 | 100,000 | 86,971 | 186,971 |
| 16 | 106,000 | 100,683 | 206,683 |
| 17 | 112,000 | 115,820 | 227,820 |
| 18 | 118,000 | 132,486 | 250,486 |
| 19 | 124,000 | 150,790 | 274,790 |
| 20 | 130,000 | 170,851 | 300,851 |
Contributions are added at the end of each month. With yearly compounding, each contribution earns simple interest until the yearly credit. The return is an assumption you choose, not a promise: real returns vary from year to year and can be negative. Fees, taxes and inflation are not included.
The calculator runs in your browser. Nothing you type is saved or sent anywhere.
Educational tool, not financial advice. The results only reflect the numbers you enter and say nothing about future returns. Trading involves a substantial risk of loss.
How to use the compound interest calculator
- Enter what you start with and what you plan to add each month. Either one can be zero.
- Enter an assumed annual return. Choose a cautious figure and try several: real returns change every year and can be negative.
- Enter the number of years and choose monthly or yearly compounding.
- Read the final balance, the total contributed and the total growth, then open the year-by-year table to see when growth overtakes your contributions.
The compound interest formula in plain words
Each period, the balance earns the return on everything already in the account, including past growth, and then the new contribution is added. Growth on growth is what makes the curve bend upward over long periods.
With monthly compounding, the annual rate is split into twelve monthly rates, and contributions are added at the end of each month. Fees, taxes and inflation are not included, so what you keep, in today’s money, would be lower.
Each month: balance = balance × (1 + annual rate ÷ 12) + contribution
Without contributions: final = start × (1 + rate ÷ n)^(n × years)
Growth = final balance − starting amount − all contributions
Worked example
$5,000 to start and $200 a month for 20 years, at an assumed 7% a year compounded monthly.
- Total contributed: $5,000 + $200 × 240 months = $53,000.
- Final balance: about $124,379.
- Growth: $124,379 − $53,000 = about $71,379, more than you paid in.
- Growth overtakes contributions in year 17, which is why the last years add the most.
- With yearly compounding instead, the final balance is about $120,894.
The 7% is an assumption for the example, not a forecast.
Questions
What annual return should I use?
One you can justify, not one you hope for. Broad stock indexes have had long stretches of strong and weak returns, and the past does not set the future. Run the calculator with a low, a middle and a high figure to see a range rather than a single answer.
Monthly or yearly compounding: does it matter?
A little. 7% a year compounded monthly equals about 7.23% compounded yearly. Over decades the gap adds up, but the return you assume matters far more.
Does the calculator include inflation?
No. The result is in future dollars. To think in today’s money, subtract an assumed inflation rate from the return, for example 7% − 3% = about 4% in real terms.
What is the rule of 72?
A shortcut: divide 72 by the annual return to estimate how many years it takes to double. At 8% a year, money doubles in about 9 years. The compound interest lesson explains why it works.
UpTickFlow is our product. These guides are education, not financial advice. Trading involves a substantial risk of loss.