Compound interest calculator
Enter a starting amount, a monthly addition, a rate and a number of years, and see the balance grow year by year on a chart. It shows how much came from your deposits and how much from growth.
Balance after 30 years
You put in $190,000. Compounding adds $501,150 on top, 73% of the final balance.
Year-by-year breakdown
| Year | Put in so far | Growth so far | 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 |
| 21 | $136,000 | $192,796 | $328,796 |
| 22 | $142,000 | $216,760 | $358,760 |
| 23 | $148,000 | $242,892 | $390,892 |
| 24 | $154,000 | $271,345 | $425,345 |
| 25 | $160,000 | $302,290 | $462,290 |
| 26 | $166,000 | $335,905 | $501,905 |
| 27 | $172,000 | $372,384 | $544,384 |
| 28 | $178,000 | $411,934 | $589,934 |
| 29 | $184,000 | $454,777 | $638,777 |
| 30 | $190,000 | $501,150 | $691,150 |
How this calculator works
Enter what you start with, what you add each month and the yearly return you expect. Each month the balance earns one twelfth of the yearly rate, then your deposit is added.
The chart splits the balance into the money you put in and the growth on top. Over long periods, growth usually ends up larger than your own deposits, which is the whole point of starting early.
Balance each month = previous balance × (1 + rate ÷ 12) + monthly depositCommon questions
What return should I use?
Many people plan with 6–7% a year for a stock-heavy portfolio, which is below the long-run average of the S&P 500 to leave room for bad decades. Use 4–5% for a savings account or bonds.
Is compound interest the same for stocks?
Stocks do not pay interest, but reinvested gains and dividends compound the same way. The calculator treats the return as a steady average; real returns arrive unevenly.
Does this include inflation or taxes?
No. To see results in today's dollars, subtract expected inflation from the return (for example, 7% − 3% = 4%).
FatDCA calculators are educational estimates, not investment, tax or legal advice. Results depend on the assumptions you enter, and past returns do not predict future returns.
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