Compound Interest Calculator
By Miikka · CalcBrew · Updated
Principal
$10,000.00
Total interest
+$6,470.09
Final amount
$16,470.09
Yearly growth
Yearly growth
| Year | Value | Interest |
|---|---|---|
| 1 | $10,511.62 | +$511.62 |
| 2 | $11,049.41 | +$1,049.41 |
| 3 | $11,614.72 | +$1,614.72 |
| 4 | $12,208.95 | +$2,208.95 |
| 5 | $12,833.59 | +$2,833.59 |
| 6 | $13,490.18 | +$3,490.18 |
| 7 | $14,180.36 | +$4,180.36 |
| 8 | $14,905.85 | +$4,905.85 |
| 9 | $15,668.47 | +$5,668.47 |
| 10 | $16,470.09 | +$6,470.09 |
This compound interest calculator shows how an investment grows over time as returns earn further returns. It suits anyone who wants to understand why time and the rate of return matter so much in investing.
How the calculator works and what it’s for▾
What compound interest means
Compounding happens when returns earned earlier stay invested and begin to generate returns of their own. Over time growth accelerates, because returns accrue on an ever-larger base.
A longer holding period can multiply the final amount many times over the starting capital, even if the annual return stays the same.
What you enter and what you get
Enter the starting capital, the expected annual return and the investment period in years. The calculator returns the final amount and how much of it is accumulated return.
You can try different rates and time spans to see how they shape the outcome.
Who finds it useful
It works for new investors learning the logic of compounding and for more experienced planners who want a quick picture of long-term growth.
Worth remembering
The calculator assumes a steady annual return, while real market returns vary from year to year. Use a realistic assumption and remember that inflation and taxes reduce your real purchasing power.
🔄 Reviewed June 2026
The compound interest formula
P is the starting principal, r the annual rate as a decimal, n the number of compounding periods per year, t the number of years and PMT a deposit made every period. Worked example: $10,000 at 5% compounded monthly for 10 years grows to 10,000 × (1 + 0.05 ÷ 12)^120 = $16,470. Simple interest would have paid $5,000; compounding adds another $1,470 because each month’s interest starts earning interest itself.
$10,000 at 5%: how time and compounding frequency change the result
| Years | Simple interest | Yearly | Monthly | Daily |
|---|---|---|---|---|
| 5 | $12,500 | $12,763 | $12,834 | $12,840 |
| 10 | $15,000 | $16,289 | $16,470 | $16,487 |
| 20 | $20,000 | $26,533 | $27,126 | $27,181 |
| 30 | $25,000 | $43,219 | $44,677 | $44,812 |
| 40 | $30,000 | $70,400 | $73,584 | $73,880 |
Time does far more than frequency. Going from yearly to daily compounding adds about 1% to the balance after 10 years, while another 10 years of growth adds over 60%. Most US savings accounts and CDs compound daily and credit interest monthly; the advertised APY already includes that effect, so enter either the APY with yearly compounding or the APR with the bank’s actual frequency, not both.
Regular deposits: where most of the growth comes from
A single deposit is rare in practice; most people add money every month. Depositing $200 a month at 7% for 30 years puts in $72,000 of your own money and ends at about $243,994. Starting ten years later, with the same $200 a month, ends at $104,185: the last decade of compounding is worth more than all the deposits combined. The savings calculator lets you set a goal and find the monthly deposit that reaches it.
Rule of 72 and APR vs. APY
Divide 72 by the annual rate to estimate the doubling time: 72 ÷ 6 = 12 years at 6%, 72 ÷ 9 = 8 years at 9%. The Rule of 72 calculator shows how far the shortcut drifts at very high or low rates. APR is the plain annual rate; APY (annual percentage yield) is what you actually earn after compounding: 5% APR compounded monthly is an APY of (1 + 0.05 ÷ 12)^12 − 1 = 5.12%. Compare accounts by APY, and use the APY calculator to convert between the two.
Frequently asked questions
Cite this calculator
CalcBrew. (2026). Compound Interest. https://calcbrew.com/compound-interest-calculator“Compound Interest.” CalcBrew, 2026, calcbrew.com/compound-interest-calculator.Link to https://calcbrew.com/compound-interest-calculator. Results are estimates; cite the underlying formula or data source for academic work.
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