Compound Interest Calculator
Free compound interest calculator. Enter principal, rate, time and compounding frequency to see the maturity amount and total interest earned instantly.
About the Compound Interest Calculator
A compound interest calculator that shows how much a principal grows when interest earns interest, for any rate, period and compounding frequency (yearly, half-yearly, quarterly or monthly).
Compound interest is interest calculated on both your original principal and the interest already earned — the mechanism behind nearly all long-term wealth building, from fixed deposits to equity returns. Where simple interest grows your money in a straight line, compounding curves upward: the growth itself starts growing. This calculator shows the effect precisely for any principal, rate, period and compounding frequency.
The formula is A = P × (1 + r/m)^(m×t), where P is the principal, r the annual rate, m the number of compounding periods per year and t the time in years. Frequency matters: ₹1 lakh at 8% for 10 years becomes ₹2.16 lakh compounded yearly, but ₹2.22 lakh compounded monthly. The more often interest is credited, the earlier it starts earning its own interest.
Two practical uses. First, comparing products: banks quote nominal rates with different compounding — converting them to maturity values makes offers directly comparable. Second, appreciating time: at 8%, money doubles roughly every 9 years (the rule of 72 — divide 72 by the rate). Starting ten years earlier doesn't add a little, it roughly doubles the outcome. Play with the time field and watch how disproportionately the final amount responds — that's the argument for starting to invest now rather than at a 'better' time.
How to use the Compound Interest Calculator
- Enter your basic details in the fields provided.
- Select the appropriate options from the dropdowns.
- View your precise calculation results instantly.
Worked example
₹1,00,000 at 8% for 10 years → ₹2,15,892.50 (interest ₹1,15,892.50) compounded yearly, but ₹2,21,964.02 (interest ₹1,21,964.02) compounded monthly.
Formula
A = P × (1 + r/m)^(m×t), where P is the principal, r the annual rate (÷ 100), m the compounding periods per year and t the time in years.Frequently asked questions
- What's the difference between simple and compound interest?
- Simple interest is charged only on the original principal every period. Compound interest is charged on principal plus accumulated interest, so the amount grows faster — dramatically so over long periods.
- What is the rule of 72?
- A mental shortcut: divide 72 by the annual rate to estimate how many years money takes to double. At 8%, roughly 9 years; at 12%, roughly 6 years.
- Does compounding frequency really matter?
- Yes, though moderately. More frequent compounding gives a higher effective yield for the same nominal rate — 8% compounded monthly is an effective 8.30% a year. Always compare effective yields, not headline rates.
- Is my financial data secure?
- Absolutely. All calculations happen entirely in your browser and none of your inputs are saved or sent to any server.
- Can I use this for official tax filing?
- While highly accurate for planning and estimation, always consult your CA or tax professional for final official filings.
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