Compound Interest Calculator
See how your investments grow exponentially over time. Includes initial capital, monthly contributions, and a full year-by-year breakdown.
Parameters
Final value
$426,404.61
Total invested
$130,000.00
Total interest
$296,404.61
Balance over time
Period breakdown
| Period | Balance | Invested | Interest |
|---|---|---|---|
| Start | $10,000.00 | $10,000.00 | $0.00 |
| Year 1 | $17,270.27 | $16,000.00 | $1,270.27 |
| Year 2 | $25,267.56 | $22,000.00 | $3,267.56 |
| Year 3 | $34,064.59 | $28,000.00 | $6,064.59 |
| Year 4 | $43,741.32 | $34,000.00 | $9,741.32 |
| Year 5 | $54,385.72 | $40,000.00 | $14,385.72 |
| Year 6 | $66,094.55 | $46,000.00 | $20,094.55 |
| Year 7 | $78,974.28 | $52,000.00 | $26,974.28 |
| Year 8 | $93,141.97 | $58,000.00 | $35,141.97 |
| Year 9 | $108,726.44 | $64,000.00 | $44,726.44 |
| Year 10 | $125,869.35 | $70,000.00 | $55,869.35 |
| Year 11 | $144,726.56 | $76,000.00 | $68,726.56 |
| Year 12 | $165,469.48 | $82,000.00 | $83,469.48 |
| Year 13 | $188,286.70 | $88,000.00 | $100,286.70 |
| Year 14 | $213,385.63 | $94,000.00 | $119,385.63 |
| Year 15 | $240,994.47 | $100,000.00 | $140,994.47 |
| Year 16 | $271,364.18 | $106,000.00 | $165,364.18 |
| Year 17 | $304,770.87 | $112,000.00 | $192,770.87 |
| Year 18 | $341,518.22 | $118,000.00 | $223,518.22 |
| Year 19 | $381,940.31 | $124,000.00 | $257,940.31 |
| Year 20 | $426,404.61 | $130,000.00 | $296,404.61 |
What is compound interest?
Compound interest means that the interest you earn in one period is added to your principal, so in the next period you earn interest on a larger base. This creates exponential growth: the longer your time horizon, the more dramatic the effect.
Which rate should I use?
The S&P 500 has historically returned ~10%/year before inflation over long periods — use this for an all-equity US index fund scenario. A balanced growth portfolio (stocks + bonds) is closer to 7%. High-yield savings accounts (HYSA) are currently paying around 4–5% with FDIC insurance and zero market risk. Bonds historically return ~4% annualized.
Formula used
FV = PV × (1+r)^n + PMT × ((1+r)^n − 1) / rwhere r is the monthly rate, n is the number of months, PV is the initial investment, and PMT is the monthly contribution. Annual rates are converted to monthly viar = (1 + annual%)^(1/12) − 1.
For educational purposes only. Not financial advice. Past returns do not guarantee future results.