Compound Interest Calculator
Enter a starting amount, a rate and a time to see what compound interest does to a balance. Add regular deposits if you want, and compare how often the interest is compounded.
Last updated November 3, 2026
Result
Balance after 10 years = $16,470.09
| Result | Value |
|---|---|
| Final balance | $16,470.09 |
| Total deposited | $10,000.00 |
| Interest earned | $6,470.09 |
| Effective annual yield (APY) | 5.116% |
| Year | Deposited | Interest | Balance |
|---|---|---|---|
| Year 1 | $10,000.00 | $511.62 | $10,511.62 |
| Year 2 | $10,000.00 | $1,049.41 | $11,049.41 |
| Year 3 | $10,000.00 | $1,614.72 | $11,614.72 |
| Year 4 | $10,000.00 | $2,208.95 | $12,208.95 |
| Year 5 | $10,000.00 | $2,833.59 | $12,833.59 |
| Year 6 | $10,000.00 | $3,490.18 | $13,490.18 |
| Year 7 | $10,000.00 | $4,180.36 | $14,180.36 |
| Year 8 | $10,000.00 | $4,905.85 | $14,905.85 |
| Year 9 | $10,000.00 | $5,668.47 | $15,668.47 |
| Year 10 | $10,000.00 | $6,470.09 | $16,470.09 |
A projection at a fixed rate. Real rates change, and taxes and fees are not included.
Show the work
Formula: Balance = P × G^months + deposits grown by G each month, where G = (1 + rate ÷ n)^(n ÷ 12) and n is the number of compounding periods per year.
- You entered $10,000.00 at 5% a year, compounded monthly, for 10 years (120 months).
- Growth factor per month: G = (1 + 5% ÷ 12)^(12 ÷ 12) = 1.00416667.
- Starting amount grows to $10,000.00 × G^120 = $16,470.09.
- Total deposited: $10,000.00 = $10,000.00. Interest: $16,470.09 − $10,000.00 = $6,470.09.
Result: Balance after 10 years = $16,470.09
The compound interest formula
A = P × (1 + r ÷ n)^(n × t)
P is the starting amount, r the yearly rate as a decimal, n the number of times interest is compounded per year and t the time in years. A is the balance at the end. Interest is added to the balance every period, so later interest is earned on earlier interest. With continuous compounding the formula becomes A = P × e^(r × t).
Regular deposits use the future value of an annuity: each deposit grows for the months it stays invested. The calculator converts your rate into a growth factor per month, G = (1 + r ÷ n)^(n ÷ 12), and applies it month by month. For a lump sum that equals the formula above exactly. A deposit at the end of a period earns interest from the next period, while a deposit at the start earns for the whole period.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: Loan Payment Calculator, Annuity Calculator and Retirement Calculator.
How compounding frequency changes the result
The more often interest is added, the more the balance grows, but the gain shrinks quickly. $10,000 at 5% for 10 years becomes $16,288.95 compounded annually, $16,386.16 semiannually, $16,436.19 quarterly, $16,470.09 monthly and $16,486.65 daily. Continuous compounding, the mathematical limit, gives $16,487.21.
The yearly rate you quote (the APR) is not the rate you actually earn. The effective annual yield, or APY, folds compounding in. At 5% compounded monthly the APY is 5.116%.
Adding regular deposits
Deposits often matter more than the starting amount. Saving $200 a month at 6% compounded monthly, deposited at the end of each month, grows to $2,467.11 after 1 year, $13,954.01 after 5 years, $32,775.87 after 10 years and $92,408.18 after 20 years. Over 20 years you deposit only $48,000, so most of the final balance is interest.
Choose the start of the period to model a deposit made on the first day of the month or year. It earns one extra period of interest, which raises the balance slightly.
Time matters more than the rate
Because growth builds on itself, the last years add the most. In the worked example below, the balance gains $511.62 in year 1 but $17,551.04 between year 20 and year 30. Starting ten years earlier at the same rate usually beats raising the rate by a point or two, which is why the calculator accepts up to 100 years.
Estimating doubling time
A quick mental check is the rule of 72: divide 72 by the rate to estimate the years needed to double. At 6% that is about 12 years. It is an approximation that works best for rates between roughly 6% and 10%. For an exact answer, put your own rate and a starting amount in the calculator and read the balance by year.
General information, not financial advice
This calculator gives a general estimate from the numbers you enter. It is not financial or tax advice, and your actual results can differ. Check important decisions with a qualified professional or the official source.
Sources
Official and primary sources for the statements on this page. Their authors have not reviewed or endorsed this page.
- U.S. Securities and Exchange Commission, Investor.gov, Compound Interest (glossary).. Defines compound interest as interest paid on principal and on accumulated interest.
- U.S. Securities and Exchange Commission, Investor.gov, What is compound interest?. Gives a compound-interest example and explains the Rule of 72 as an approximate way to estimate how long an investment takes to double.
How to use the Compound Interest Calculator
- Enter your starting amount and, if you save regularly, the deposit, its frequency and its timing.
- Enter the yearly interest rate and choose how often it is compounded.
- Enter the years and any extra months, up to 100 years.
- Read the balance, the interest and the table by year, open Show the work, then Copy, Print or Share.
Worked example
You invest $10,000 at 5% a year compounded monthly with no deposits. Each month the balance is multiplied by 1 + 0.05 ÷ 12 = 1.0041667. After 10 years that is 10,000 × 1.0041667^120 = $16,470.09, so the interest earned is $6,470.09.
| Years | Balance |
|---|---|
| 1 | $10,511.62 |
| 5 | $12,833.59 |
| 10 | $16,470.09 |
| 20 | $27,126.40 |
| 30 | $44,677.44 |
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is paid only on the original amount. Compound interest is paid on the original amount plus the interest already added, so the balance grows faster each period.
Is a higher compounding frequency always better?
It always gives a slightly higher balance at the same stated rate, but the difference is small. Moving from monthly to daily compounding at 5% adds only a few dollars on $10,000 over ten years.
Can I use this calculator with a 0% rate?
Yes. With a 0% rate no interest is earned, so the balance is the starting amount plus the deposits you make.
Does the result include taxes or inflation?
No. It shows the nominal balance at a fixed rate. Taxes, fees and inflation all reduce what the money is worth to you, and real rates change over time.