Investing
Compound Interest Calculator
See how your money grows with the power of compounding. Real-time results with interactive charts.
Parameters
Monthly deposits use the selected timing and an equivalent monthly growth rate. Fees reduce annual growth proportionally. Projections are assumptions, exclude tax and inflation, and are not guaranteed returns.
Growth Over Time
Balance Breakdown
Understanding Compound Interest
The Core Concept
Compound interest is interest calculated on the initial principal *and* on the accumulated interest from previous periods. This creates exponential growth over time, unlike simple interest which grows linearly.
Why It Matters in the AI Economy
Capital is being deployed at unprecedented speed into AI infrastructure, chips, and software. Understanding compounding helps you evaluate whether today's high valuations can be justified by decades of future cash flow growth.
Real-World Example
Investing $500/month for 40 years under an assumed 8% nominal annual return with monthly compounding and end-of-month deposits turns $240,000 in total contributions into roughly $1.75 million before fees, taxes and inflation. The majority of that growth happens in the last 10–15 years due to the power of compounding.
Pro Tips from Long-Term Investors
- Start early: Time is the most powerful factor. 10 extra years can more than double your outcome.
- Increase contributions over time: As your income grows (common in tech/AI careers), raise your monthly amount annually.
- Minimize fees: A 1% difference in fees over 30+ years can cost hundreds of thousands of dollars.
- Reinvest everything: Let dividends and interest buy more assets instead of taking cash distributions early.
View chart data
| Year | Balance | Contributions | Interest |
|---|---|---|---|
| 0 | 10,000 | 10,000 | 0 |
| 1 | 17,055 | 16,000 | 1,055 |
| 2 | 24,695 | 22,000 | 2,695 |
| 3 | 32,970 | 28,000 | 4,970 |
| 4 | 41,932 | 34,000 | 7,932 |
| 5 | 51,637 | 40,000 | 11,637 |
| 6 | 62,148 | 46,000 | 16,148 |
| 7 | 73,531 | 52,000 | 21,531 |
| 8 | 85,859 | 58,000 | 27,859 |
| 9 | 99,210 | 64,000 | 35,210 |
| 10 | 113,669 | 70,000 | 43,669 |
| 11 | 129,329 | 76,000 | 53,329 |
| 12 | 146,288 | 82,000 | 64,288 |
| 13 | 164,655 | 88,000 | 76,655 |
| 14 | 184,546 | 94,000 | 90,546 |
| 15 | 206,088 | 100,000 | 106,088 |
| 16 | 229,419 | 106,000 | 123,419 |
| 17 | 254,685 | 112,000 | 142,685 |
| 18 | 282,049 | 118,000 | 164,049 |
| 19 | 311,684 | 124,000 | 187,684 |
| 20 | 343,778 | 130,000 | 213,778 |
Assumptions and disclaimer
Calculator outputs are educational estimates, not financial, investment, tax, or legal advice. Results depend on the inputs and assumptions shown on the page and may exclude fees, state rules, market volatility, liquidity, or timing effects. Verify figures with current sources and consult a qualified professional before making decisions.
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How to use it
- 1Enter the starting amountType the money already saved and the amount you add each month.
- 2Set a rate and a spanChoose an annual rate, how often it compounds, and how many years to run.
- 3Read the splitThe result separates what you put in from the interest the rate produced.
Questions people ask
- How is compound interest calculated?
- The calculator converts the nominal annual rate at the selected compounding frequency into an equivalent monthly growth rate. Monthly deposits stay monthly and use the selected start- or end-of-month timing. An annual fee, when entered, reduces that growth proportionally. With the fee at 0%, $10,000 starting, $500 added each month, 8% nominal annual compounded monthly, and 20 years is about $343,778.24 before fees.
- How often should I compound?
- Monthly deposits are not grouped into the compounding period. Whatever frequency you pick, the nominal annual rate becomes an equivalent monthly growth rate and deposits stay monthly. Daily compounding changes the result only slightly versus monthly at typical rates. A 0% rate returns only the cash you put in.
- Does this include taxes or fees?
- Taxes and inflation are excluded. The annual fee field is included: it reduces annual growth proportionally. Leave the fee at 0% for the result before fees. The figure is an educational estimate, not a guaranteed return.