See how savings and monthly deposits grow with compound interest, with a chart and a year-by-year table.
Quick answer
With interest compounded monthly, $10,000 grows to $20,096.61 after 10 years. That is $10,096.61 of interest, about 2.01 times the original amount.
| Years | 5% a year | 7% a year | 9% a year |
|---|---|---|---|
| 5 | $12,834 | $14,176 | $15,657 |
| 10 | $16,470 | $20,097 | $24,514 |
| 20 | $27,126 | $40,387 | $60,092 |
| 30 | $44,677 | $81,165 | $147,306 |
These figures are computed with the same formulas as the Compound Interest Calculator above. Change the inputs in the tool to see your own result. For a full table, see Compound interest table and Inflation table.
The Compound Interest Calculator shows how a starting amount and regular monthly contributions grow over time when interest earns interest. Choose the compounding frequency (annual to daily), whether you deposit at the start or end of each month, and see the final balance, total deposits, interest earned, a growth chart and a year-by-year table. Set the contribution to zero to see the classic A = P(1 + r/n)^(nt) result.
Made for everyone. Typical uses:
$10,000 invested with $200 added every month at 6% compounded monthly grows to $125,510.22 after 20 years. You put in $58,000 ($10,000 plus 240 × $200), so $67,510.22 of the balance is interest. With no monthly contributions, $10,000 at 5% compounded monthly for 10 years becomes $16,470.09.
The calculator assumes a constant rate, no taxes, no fees and no inflation. Real returns vary from year to year, so treat the result as a comparison tool rather than a forecast.
Accuracy: Formulas follow standard published methods and are checked against worked reference examples. Results are estimates based on the values you enter and do not replace advice from a qualified professional.
Expert Tip
Run the same principal and timeframe at a couple of different interest rates or compounding frequencies side by side -- small rate differences compound into surprisingly large gaps over 15-20+ years.
Simple interest pays only on your original amount. Compound interest also pays on the interest you have already earned, so growth accelerates. The formula for a lump sum is A = P(1 + r/n)^(nt), where P is the starting amount, r the yearly rate, n the number of compounding periods per year and t the number of years. With regular deposits the calculator adds each deposit and compounds it too.
The effect is small at first and enormous later. $10,000 growing at 6 percent, compounded monthly, becomes $33,102 after 20 years without adding a cent. At 3 percent the same money reaches $18,208, and at 9 percent it reaches $60,092. Tripling the rate does not triple the result; it multiplies it several times, because each year builds on the last.
Adding a monthly amount changes the picture. $10,000 plus $200 a month at 6 percent for 20 years grows to $125,510. You paid in $58,000 ($10,000 plus 240 deposits of $200), so $67,510 is interest. A steady habit contributes more than a large one-off, and the calculator shows deposits and interest separately so you can see how much of the balance you earned rather than saved.
Timing inside the month matters slightly. Depositing at the start of each month earns one extra month of interest per deposit compared with depositing at the end, which is why the calculator lets you choose. If your salary arrives at the end of the month and you invest immediately, choose end; if you set an automatic transfer on the first, choose start.
Time is the most powerful input. Invest $200 a month at 7 percent for 40 years and you end with about $524,963. Start ten years later and invest for 30 years and you end with about $243,994. The extra ten years contributed only $24,000 more in deposits but produced $281,000 more in the final balance. Waiting a decade to start cuts the outcome by more than half, even though you save the same amount each month.
The lesson is not to fear waiting too long but to start with whatever amount you can. A smaller amount begun now often beats a larger amount begun later. As your income grows, raise the monthly figure and rerun the calculation.
Slightly, and less than most people expect. $10,000 at 5 percent for 10 years becomes $16,288.95 compounded once a year, $16,470.09 monthly and $16,486.65 daily. The gap between annual and daily compounding is under $200 on a 10-year investment, while a single percentage point in the rate would change the result by over $1,500. Focus on the rate, the time and your contribution before you worry about the compounding schedule.
When comparing accounts, look for the APY (annual percentage yield), which already includes compounding and lets you compare different frequencies fairly.
To estimate how long it takes money to double, divide 72 by the annual rate. At 6 percent that is about 12 years (the exact figure is 11.9), and at 3 percent about 24 years (exactly 23.45). The rule works best for rates between about 4 and 12 percent. It also works in reverse for debt: a credit card at 24 percent doubles what you owe in about three years if you make no payments.
The calculator assumes a constant rate, no taxes, no fees and no inflation. Real returns vary year by year, and savings accounts, bonds and stocks behave very differently. To see what the final amount will really buy, check it against the Inflation Calculator. If you want to know the growth rate of an investment you already have, use the CAGR Calculator, and to plan a specific target use the Savings Goal Calculator. The article how compound interest works explains the idea from the beginning, and simple vs compound interest compares the two.
Compound interest explained step by step: the formula, why time matters more than the rate, how monthly deposits change the result, and how to test your own numbers.
Learn the ROI formula, how to annualize a return, what to count as cost, and how ROI applies to stocks, property and marketing, with worked examples.
The difference between simple and compound interest with formulas, side-by-side numbers over 3, 10 and 30 years, and how to tell which one your loan or account uses.
Reference table with CSV download.
Reference table with CSV download.
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