Compound interest calculator
Compound interest is interest earned on both your starting amount and interest already added. Choose an annual rate, a term, and a compounding frequency to estimate how a balance may grow.
Updated ·Sources verified
Enter a starting amount, annual rate, whole-year term, compounding frequency, and an optional contribution. You will see the final balance, money paid in, total interest, and a year-by-year chart. A contribution is added at the end of each chosen compounding period.
Final balance
$31,998.32
- Total paid in (starting amount + contributions)
- $22,000.00
- Regular contributions (excluding starting amount)
- $12,000.00
- Total interest
- $9,998.32
What changes your savings?
Current inputs (USD)
- Final balance
- $31,998
- Total paid in
- $22,000
- Interest
- $9,998
Extra $1,200 per year, divided across chosen periods (USD)
- Final balance
- $47,527
- Total paid in
- $34,000
- Interest
- $13,527
Five more years (USD)
- Final balance
- $47,866
- Total paid in
- $28,000
- Interest
- $19,866
The extra amount is divided across your chosen compounding periods and paid at each period end. It matches the yearly amount of 100 per month, but not the timing unless you choose monthly compounding. The rate is unchanged; tax, fees, and inflation are not included.
Each bar shows the balance at the end of a year: deposits at the bottom and interest above. At a positive rate, interest can build on interest already earned.
How does it work?
A contribution is paid at the end of each chosen period. It is monthly only when you choose monthly compounding. At 0%, the final balance is simply the starting amount plus all contributions.
Compound interest formula
- FV
- Final balance at the end.
- P
- Starting amount.
- r
- Annual interest rate, written as a decimal in the formula.
- n
- Number of compounding periods each year.
- t
- Number of years.
- PMT
- Contribution made at the end of each compounding period.
10,000 at 5% compounded monthly for 10 years grows to about 16,470 with no extra deposits.
Method & sources
This is a planning estimate based on the starting amount, contribution, term, and rate you enter. It does not know the rate you will actually receive.
Sources
Where this method comes from — use these references to understand the formula, assumptions, and limits.
- Compound Interest — U.S. Securities and Exchange Commission (Investor.gov), verified 2026-09-27
How we calculate
- The interest rate stays the same for the whole term.
- Contributions are added at the end of each compounding period.
- Taxes, fees, and inflation are not included.
- Results are estimates for planning, not a forecast or financial advice.
Rounding
Balances are rounded to two decimals for display. The calculation uses full precision.
What this calculator does
The calculator applies a fixed annual rate to your starting amount and adds interest at the frequency you choose. It can also include a regular contribution, added at the end of every compounding period.
How to use it
- Enter your starting amount.
- Enter the annual interest rate as a percentage.
- Choose a whole number of years from 1 to 100 and how often interest compounds.
- Add the amount you plan to contribute at the end of each period. It is monthly only when you choose monthly compounding.
A worked example
Start with 10,000 at 5% compounded monthly for 10 years. With no extra deposits, the balance becomes about 16,470.09. Add 100 at the end of every month and it becomes about 31,998.32. Of that amount, 22,000 is deposited money and about 9,998.32 is interest.
What the result means
The final balance is the starting amount and all contributions, plus the interest earned. A longer term can give compounding more time to work. If you change the compounding frequency, remember that the same contribution is then paid a different number of times.
Common mistakes
- Entering a monthly rate in the annual rate field. Use the yearly rate.
- Comparing compounding frequencies while leaving the contribution unchanged. The contribution is made once per period, so the total paid in changes too.
- Expecting a fixed rate to match real-world returns, which can vary.
- Forgetting that inflation reduces what the final balance can buy.
When it's useful
Use it to sketch out long-term saving, see how a term and a fixed rate affect a balance, or test the effect of regular contributions. To compare compounding frequencies fairly, keep total contributions the same.
FAQ
- What is compound interest?
- It is interest calculated on both your original amount and the interest already added. Over time the balance grows faster than with simple interest.
- How does compounding frequency change the result?
- With no contributions, more frequent compounding adds interest sooner, so it can produce a slightly higher balance at the same annual rate. If you enter a contribution, it is also made once per period; compare equal total contributions to isolate the frequency effect.
- How are contributions handled?
- Each contribution is added at the end of a compounding period. It earns interest only in the periods that follow before the term ends.
- Does this include tax or inflation?
- No. The result is before tax and fees and is not adjusted for inflation, so the real spending power may be lower.
- What rate should I use?
- Choose a rate that you consider a reasonable planning assumption for your savings or investment. Actual returns can vary from year to year.
- Can I save or share my result?
- Yes. You can copy, share a link that reopens the same scenario, download a text summary, or print the page.
Related calculators
- Simple interest calculatorCompare against interest that does not compound.
- Inflation calculatorSee what the final balance is worth after inflation.
- Savings CalculatorA savings plan with monthly compounding and a monthly deposit, with money paid in and interest shown separately.
- Rule of 72 calculatorQuickly estimate how long money takes to double.
- Investment return calculatorWork out the total and annual return on an investment.
Read more on the blog
- How much does inflation really erode your savings? Use official CPI rates (2026)Stop guessing at an inflation rate. WiseCalcs now ships annual U.S. CPI-U figures from the Bureau of Labor Statistics as one-click presets — plus a 10-year history table — so you can see what today's dollars are worth in 5, 10, or 20 years.
- Complete 2026 Tax Guide: Tax Brackets, Paycheck Calculators, and Payroll Changes That Actually MatterYour paycheck is about to look a little different in 2026. With updated federal tax brackets, a higher Social Security wage base, and new standard deduction amounts, there's real money on the line here. We'll break down exactly what the changes mean for your take-home pay, show you how to calculate your after-tax income, and help you make smarter decisions with your money this year.
- US Inflation Is Crushing Your Savings: Here's How Britons Can Fight BackAmerican inflation might seem like someone else's problem, but when the world's largest economy sneezes, Britain catches a cold. With US inflation rippling through global markets and affecting everything from your weekly shop to your pension pot, protecting your British savings has never been more crucial.
- Inflation's Impact on Retirement Savings 2026: Protect Your FutureCurrent inflation trends are quietly eroding retirement savings purchasing power. Learn how to calculate real returns and protect your future with inflation-resistant strategies.
Embed this calculator
Add this calculator to your own site. The snippet includes the calculator iframe and a small attribution link:
<iframe src="https://wisecalcs.com/embed/en/compound-interest-calculator" width="100%" height="520" style="border:0" loading="lazy"></iframe>
<p>Calculator from <a href="https://wisecalcs.com/en/investments-retirement/compound-interest" rel="nofollow noopener">WiseCalcs</a></p>