Compound Interest Calculator
Enter a starting amount, an annual rate, a number of years, and how often interest compounds to see the final balance.
Compound Interest Calculator calculates in your browser.
See how compound interest grows a balance
Compound interest earns interest on earlier interest as well as on the original amount, so growth speeds up over time. Enter a starting amount, an annual rate, a number of years, and a compounding frequency to see the final balance, the interest earned, the total growth, and the effective annual rate — for example, $1,000.00 at 5% compounded monthly for 10 years grows to $1,647.01. The result illustrates the formula at one fixed rate; it is not a forecast of what an account or investment will earn.
How to use the Compound Interest Calculator
- Type the starting amount (the principal). $0 is allowed but has nothing to grow.
- Type the annual interest rate and the number of years. Years can be a decimal, such as 2.5.
- Choose how often interest compounds: annually, semiannually, quarterly, monthly, or daily.
- Read the final balance, interest earned, total growth, and effective annual rate, with the formula worked through underneath.
The formula
A = P(1 + r/n)^(nt)
interest = A − P · effective annual rate = (1 + r/n)^n − 1
P is the starting amount, r the annual rate as a decimal (5% is 0.05), n the number of compounding periods per year, and t the number of years. Daily compounding uses 365 periods a year. The calculation keeps full precision throughout and rounds only the displayed amounts to the cent. The table shows $1,000 at 5% for 10 years: compounding more often helps, but each step up adds less.
| Compounded | Balance after 10 years | Effective annual rate |
|---|---|---|
| Annually | $1,628.89 | 5% |
| Semiannually | $1,638.62 | 5.0625% |
| Quarterly | $1,643.62 | 5.0945% |
| Monthly | $1,647.01 | 5.1162% |
| Daily | $1,648.66 | 5.1267% |
Calculated on your device
- The calculation runs in your browser as you type; nothing is sent to a server.
- Amounts, rates, and results are not sent to Looty Tools or stored.
- The calculator area is masked from session-recording analytics, so what you enter isn’t captured in recordings.
Limitations
- One starting amount only — no regular deposits or withdrawals. For regular monthly saving toward a target, see the Savings Goal Calculator.
- The rate stays fixed for the whole period; taxes, fees, and inflation are not included.
- Continuous compounding and 360-day years are not offered.
- Fractional years apply the formula to the partial period; many accounts only credit interest at the end of each full period.
- Rates from 0% to 100% and terms of up to 100 years. The $ is a display label; the math is the same in any currency.
Related calculators
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- Loan Payment CalculatorEstimate a monthly payment from amount, rate, and term.
- Savings Goal CalculatorEstimate how long it takes to reach a savings target.
Guides
- Simple vs. Compound InterestHow simple and compound interest are calculated, how far apart they grow over time, where each is used, and the rule of 72.
- Compounding FrequencyAnnual, quarterly, monthly, and daily compounding compared, the effective annual rate, and why more frequent compounding adds less each step.
- Compound Interest FormulaEach part of A = P(1 + r/n)^(nt), a step-by-step example, rearranging it to find the starting amount or the time, and common mistakes.
Compound Interest Calculator FAQ
- What formula does the calculator use?
- A = P(1 + r/n)^(nt): P is the starting amount, r the annual rate as a decimal, n the number of times interest is compounded per year, and t the number of years. $1,000 at 5% compounded monthly for 10 years grows to $1,647.01.
- How much difference does the compounding frequency make?
- More frequent compounding earns interest on interest sooner, but the gain shrinks as the frequency rises. At 5% for 10 years, $1,000 reaches $1,628.89 compounded annually, $1,647.01 monthly, and $1,648.66 daily.
- What is the effective annual rate?
- The rate that, compounded once a year, gives the same growth: (1 + r/n)^n − 1. A 5% rate compounded monthly works out to about 5.1162% a year.
- Can I add monthly deposits?
- Not in this calculator — it shows how a single starting amount grows. To see how long regular monthly saving takes to reach a target, without interest, use the Savings Goal Calculator.
- Can I enter part of a year?
- Yes. The formula accepts fractional years, including a partial compounding period. Many accounts only credit interest at the end of each full period, so the calculator points this out when the periods don’t come out whole.
- Will an account or investment earn exactly this?
- Not necessarily. The result assumes one fixed rate for the whole time, with no deposits, withdrawals, fees, or taxes. Real rates change and investment returns are not guaranteed, so treat the result as an illustration of the math.
- Are the amounts I enter sent anywhere?
- No. The calculation runs in your browser as you type. The amounts, rates, and results are not sent to Looty Tools or stored, and the calculator area is masked from session-recording analytics. Refreshing the page clears it.
