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Compound Interest — Free Online Tool
Compound interest means you earn interest on your interest, and over many years that snowball effect is what turns regular saving into real wealth. This calculator applies annual compounding: you enter the starting principal, the yearly rate and the number of years, and it returns both the total interest earned and the final maturity amount using A = P × (1 + r/100)^t. Investing ₹10,000 at 5% for five years, for example, grows to about ₹12,763 instead of the ₹12,500 a simple-interest scheme would give. The gap widens quickly with higher rates and longer horizons, which is why starting early matters more than investing large sums later. Indian savers can use it to estimate the growth of a PPF account, whose interest is compounded annually, to check a rough fixed-deposit maturity, or to compare how long it takes for money to double at different rates. Many bank FDs compound quarterly, so their actual maturity value will be slightly higher than the annual figure shown here. The tool does not account for tax on interest, inflation or additional yearly contributions. It runs in your browser, uses no personal data and works well on a phone while you compare investment options.
Use our Compound Interest on AllConvertor — no registration, no download, works on iPhone, Android, Windows, and Mac. All processing runs in your browser when possible for maximum privacy and speed.
How to use Compound Interest
- Enter the amount you are investing as the principal.
- Add the expected annual interest rate in percent.
- Type the number of years the money will stay invested.
- Review the interest earned and the final maturity amount.
Key benefits
- ✓ 100% free — no paywall or trial limits
- ✓ No account or email required
- ✓ Mobile-friendly responsive design
- ✓ Instant results in your browser
- ✓ Secure — data stays on your device
- ✓ Trusted by thousands of users daily
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Frequently Asked Questions
What is the compound interest formula?
A = P × (1 + r/100)^t, where P is the principal, r is the annual rate in percent and t is the number of years. Compound interest equals A minus P.
How is compound interest different from simple interest?
Simple interest is calculated only on the original principal, whereas compound interest also earns interest on previously added interest, so the balance grows faster each year.
Does this calculator compound monthly or quarterly?
It compounds once a year. Many Indian bank FDs compound quarterly, so their real maturity value will be slightly higher than the figure here.
Can I use it for PPF or fixed deposits?
Yes, as an estimate. PPF interest is compounded annually, so the result is close. For an FD, use the rate and tenure from your bank and expect a small difference if it compounds quarterly. Check the latest rate with your bank or the post office.
How long will it take to double my money?
A quick rule is the Rule of 72: divide 72 by the annual rate. At 8% your money doubles in about nine years. You can confirm it by entering the values here.