Compound Interest Calculator
See how savings grow with compound interest and regular deposits, with any compounding frequency, a growth chart and a year-by-year table.
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How to use Compound Interest Calculator
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Open Compound Interest Calculator on this page. It loads right in your browser.
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Add your file, text or values and adjust the settings.
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Copy the result or download it. Nothing is uploaded or stored.
How to use it: Compound Interest Calculator
Compound interest means you earn interest on your interest. This calculator shows how an initial deposit plus regular monthly or yearly contributions grows over time at a given rate, compounded yearly, half-yearly, quarterly, monthly or daily.
You get the future balance, total deposits, interest earned, the effective annual rate (APY) and the rule-of-72 doubling time, plus a growth chart and a year-by-year table you can download as CSV.
How to use it
- Enter the initial deposit and any regular contribution (monthly or yearly).
- Set the annual interest rate and the number of years.
- Choose the compounding frequency and whether deposits are made at the start or end of each period.
- Read the future balance and the yearly breakdown, and export it if you need it.
How it is calculated
A = P × (1 + r/n)^(n·t) for the initial deposit, where r is the annual rate, n the compounding periods per year and t the years. Each contribution compounds the same way from the moment it is added.
Worked example
Start with $10,000, add $200 every month and earn 7% a year compounded monthly. After 10 years you have deposited $34,000 and the balance is about $54,700, so roughly $20,700 is interest. Leave the same plan running for 30 years and the balance grows to about $325,000, of which about $243,000 is interest. That jump is the power of compounding: in the later years the interest earns more than your deposits.
Who uses it
- Savers comparing high-yield savings accounts and fixed deposits
- Investors projecting long-term portfolio growth
- Parents planning a college fund
- Students learning how interest and time interact
Tips
- The earlier you start, the more years compounding has to work: time matters more than the rate.
- Compare savings accounts by APY, not by the nominal rate, because compounding frequency changes the real return.
- Divide 72 by the interest rate to estimate how many years it takes for money to double.
Free, private and instant: every calculation runs in your browser, nothing is uploaded or stored, and there is no sign-up or limit. Related calculators: SIP calculator, mortgage calculator, percentage calculator.
Features
- Monthly or yearly contributions
- Yearly to daily compounding
- Deposits at the start or end of the period
- APY and rule-of-72 doubling time
- Growth chart and CSV table
Frequently asked questions
What is the compound interest formula?
A = P(1 + r/n)^(nt): P is the principal, r the annual rate, n the compounding periods per year and t the number of years.
How much does monthly compounding add?
At 5% a year, monthly compounding gives an effective 5.12% (APY) versus 5% with yearly compounding. The difference grows with higher rates and longer periods.
What is the difference between simple and compound interest?
Simple interest is earned only on the original amount; compound interest is also earned on interest already added, so the balance grows faster each year.
How long does it take to double my money?
Roughly 72 divided by the yearly rate: at 6% about 12 years, at 9% about 8 years.
Should I choose start or end of period for deposits?
If you deposit on payday at the start of the month, choose Start of period; most banks credit interest monthly, so the difference over years is small but real.
Can I use this for loans?
It shows how debt grows when nothing is repaid, such as unpaid credit-card balances. For repayment plans use the loan or EMI calculator.
Is this calculator free and private?
Yes. It is completely free, needs no account and runs entirely in your browser, so the numbers you type are never sent to a server or stored.