Compound Interest Calculator
See what savings grow to with monthly deposits, year by year.
Your numbers
Final balance
144,573
You paid in
58,000
Interest earned
86,573
Effective annual rate
7.229%
7% compounded monthly
How it grows
From year 16, interest has added more than you paid in.
Year by year
| Year | Paid in | Interest that year | Total interest | Balance |
|---|---|---|---|---|
| 1 | 12,400 | 801.42 | 801.42 | 13,201 |
| 2 | 14,800 | 1,033 | 1,834 | 16,634 |
| 3 | 17,200 | 1,281 | 3,115 | 20,315 |
| 4 | 19,600 | 1,547 | 4,662 | 24,262 |
| 5 | 22,000 | 1,832 | 6,495 | 28,495 |
| 6 | 24,400 | 2,138 | 8,633 | 33,033 |
| 7 | 26,800 | 2,466 | 11,100 | 37,900 |
| 8 | 29,200 | 2,818 | 13,918 | 43,118 |
| 9 | 31,600 | 3,196 | 17,114 | 48,714 |
| 10 | 34,000 | 3,600 | 20,714 | 54,714 |
| 11 | 36,400 | 4,034 | 24,747 | 61,147 |
| 12 | 38,800 | 4,499 | 29,246 | 68,046 |
| 13 | 41,200 | 4,998 | 34,244 | 75,444 |
| 14 | 43,600 | 5,532 | 39,776 | 83,376 |
| 15 | 46,000 | 6,106 | 45,882 | 91,882 |
| 16 | 48,400 | 6,721 | 52,603 | 101,003 |
| 17 | 50,800 | 7,380 | 59,983 | 110,783 |
| 18 | 53,200 | 8,087 | 68,070 | 121,270 |
| 19 | 55,600 | 8,845 | 76,915 | 132,515 |
| 20 | 58,000 | 9,658 | 86,573 | 144,573 |
This assumes the rate stays fixed for the whole period and ignores tax and fees. Real returns on anything other than a fixed deposit go up and down, and past returns do not predict future ones.
Private by design. This tool runs entirely in your browser. Your input is processed on your own device and is not uploaded by DO101.
About the Compound Interest Calculator
Enter a starting amount, a monthly deposit, an interest rate and a number of years, and see exactly what it grows to โ with the split between what you paid in and what the interest added, year by year. It handles every compounding frequency properly, even when your deposits are monthly and the account compounds quarterly, shows the effective annual rate and how long money takes to double, and can restate the final figure in today's money after inflation. Everything is calculated in your browser.
How to use it
- 1Enter the amount you are starting with and what you will add each month.
- 2Set the annual interest rate, how often it compounds, and the number of years.
- 3Read the final balance and how much of it is interest rather than your own money.
- 4Add an inflation rate to see what that balance is worth in today's money.
- 5Scroll the year-by-year table to see when interest starts outpacing your deposits.
What you get
- Monthly deposits with yearly, half-yearly, quarterly, monthly or daily compounding
- Correct when deposits and compounding happen at different frequencies
- Deposit at the start or end of each month
- Paid-in versus interest, as a chart and a year-by-year table
- Effective annual rate and the time it takes money to double
- Final balance in today's money, after inflation
- Calculated in your browser โ nothing is sent anywhere
Step-by-step guides
Frequently asked questions
What is compound interest?
Interest earned on interest. Each period, the interest is added to the balance, so the next period's interest is calculated on a slightly bigger number. Over long periods that snowballs: at 7% a year, money roughly doubles every ten years.
What formula does it use?
With no deposits, the standard A = P(1 + r/n)^(nt), where r is the annual rate and n the number of compounding periods a year. With monthly deposits it works month by month using the monthly rate equivalent to your compounding frequency, which gives the same answer as the formula when there are no deposits and handles deposits correctly when there are.
Does it matter how often interest compounds?
A little. More frequent compounding earns slightly more at the same stated rate, which is why the calculator shows the effective annual rate. 6% compounded monthly is about 6.17% a year; compounded daily it is about 6.18%. The rate itself and the time you leave it matter far more.
Should I deposit at the start or end of the month?
Depositing at the start means each deposit earns interest for that month too, so the result is slightly higher. Most salary-funded savings land near the start of the month; the difference is small either way.
What does 'in today's money' mean?
Inflation makes the same amount buy less over time. If you enter an inflation rate, the calculator divides the final balance by how much prices will have risen, so you can see what it would buy in today's terms.
Is this a prediction of my investment returns?
No. It assumes a fixed rate for the whole period and ignores tax and fees. That is exact for a fixed deposit, but anything invested in markets goes up and down, and past returns do not predict future ones.
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