Compound Interest Calculator – See How Your Money Grows
Enter a one-time amount, an annual interest rate, the number of years and how often interest compounds to see the maturity value and the interest earned.
What is compound interest?
With simple interest, you earn interest only on the amount you originally invested. With compound interest, the interest earned in each period is added to your balance, and the next period’s interest is calculated on that larger balance. The growth is gradual at first and then accelerates the longer the money stays invested.
Compounding is at work in bank fixed deposits, recurring deposits, PPF, small savings schemes and – in a less predictable way – in mutual funds and shares when gains are left invested. This calculator handles a single lumpsum with a fixed rate, which makes it ideal for comparing deposits or understanding how time and rate affect growth.
How is compound interest calculated?
- A = final amount (maturity value)
- P = principal invested today
- r = annual interest rate as a decimal (8% = 0.08)
- n = compounding periods per year (1 yearly, 2 half-yearly, 4 quarterly, 12 monthly)
- t = time in years
Compound interest earned = A − P.
Worked example: ₹1,00,000 at 8% for 5 years
| Compounding | Maturity value | Interest earned |
|---|---|---|
| Yearly | ₹1,46,933 | ₹46,933 |
| Half-yearly | ₹1,48,024 | ₹48,024 |
| Quarterly | ₹1,48,595 | ₹48,595 |
| Monthly | ₹1,48,985 | ₹48,985 |
For yearly compounding the working is simply ₹1,00,000 × (1.08)^5 = ₹1,46,933. Moving to monthly compounding adds about ₹2,000 over five years. Frequency matters, but far less than the rate and, above all, the time period.
Why time matters more than anything else
Keep the same ₹1,00,000 at 8% compounded yearly and only change the number of years:
- After 10 years: ₹2,15,892
- After 20 years: ₹4,66,096
- After 30 years: ₹10,06,266 – roughly ten times the original amount
With simple interest at the same 8%, ₹1,00,000 would grow to only ₹2,60,000 in 20 years. The extra ₹2,06,096 under compounding is entirely interest earned on earlier interest.
The Rule of 72
A quick mental shortcut: divide 72 by the annual rate to estimate how many years it takes money to double. At 8%, that is about 9 years (72 ÷ 8); at 6%, about 12 years. It is an approximation, but useful for comparing options quickly.
How to use this calculator
- Principal: the one-time amount you are investing or depositing.
- Rate of interest: the annual rate offered, or an assumed average return.
- Time period: how many years the money stays invested.
- Compounding frequency: match it to the product – for example, quarterly for most bank FDs.
Things the calculator does not include
- Tax: interest on FDs and most deposits is taxable at your slab rate, which lowers the effective compounding rate. PPF interest is tax-free.
- Inflation: the result is in future rupees. Check what it is worth in today’s money with the inflation calculator.
- Additional deposits: the calculator assumes a single investment. For monthly contributions, use the SIP calculator.
- Variable returns: market-linked investments do not earn a fixed rate every year, so treat results for them as illustrations only.
Compound Interest Calculator FAQs
What is compound interest?
Compound interest is interest calculated on the principal plus all interest already added to it. Because each period’s interest is added to the balance, the next period earns interest on a larger amount – “interest on interest”.
What formula does this compound interest calculator use?
A = P × (1 + r/n)^(n × t), where P is the principal, r is the annual rate as a decimal, n is the number of compounding periods per year (1, 2, 4 or 12) and t is the time in years. Compound interest = A − P.
How do I calculate compound interest step by step?
Divide the annual rate by the number of compounding periods to get the periodic rate (r/n). Multiply the balance by (1 + r/n) once for each period, n × t times in all. The final balance minus the principal is the compound interest.
What difference does compounding frequency make?
More frequent compounding gives a slightly higher result at the same headline rate. ₹1,00,000 at 8% for 5 years grows to ₹1,46,933 with yearly compounding and ₹1,48,985 with monthly compounding.
Which compounding frequency should I choose?
Match the product. Most Indian bank fixed deposits compound quarterly, PPF compounds annually, and savings accounts credit interest periodically. For market-linked investments such as mutual funds, yearly compounding at an assumed average return is a reasonable approximation.
Can I use this for mutual funds or monthly SIPs?
This calculator is for a single lumpsum investment. You can use it with an assumed return to estimate lumpsum mutual fund growth, but returns are not fixed. For regular monthly investments, use the SIP calculator instead.
Important Disclaimer
For Educational and Informational Purposes Only: This calculator is provided solely for educational and informational purposes. It is designed to help you understand potential investment outcomes and should not be considered as financial, investment, tax, or legal advice.
Not Professional Advice: The calculations, results, and information provided by this tool do not constitute professional financial advice, investment recommendations, or tax guidance. Always consult with a qualified financial advisor, certified financial planner, tax consultant, or legal professional before making any investment or financial decisions.
Accuracy and Assumptions: While we strive to ensure the accuracy of our calculators, the results are based on the inputs you provide and certain assumptions. Actual returns, interest rates, tax implications, and other factors may vary significantly based on market conditions, government policies, individual circumstances, and other variables beyond our control.
No Guarantees: Past performance is not indicative of future results. The calculations provided are estimates and projections only. We make no guarantees, warranties, or representations regarding the accuracy, completeness, or reliability of the information or calculations provided.
Regional Variations: Financial regulations, tax laws, interest rates, and investment rules vary significantly by country, state, and jurisdiction. The information provided may not be applicable to your specific location or circumstances. Always verify current rates, rules, and regulations with official sources or local authorities.
Tax Implications: Tax laws are complex and subject to change. The tax-related information provided is general in nature and may not apply to your specific situation. Consult a qualified tax professional for advice tailored to your individual circumstances.
Market Risks: All investments carry risk, including the potential loss of principal. Market conditions, economic factors, and other variables can significantly impact investment performance. Diversification and asset allocation do not guarantee profit or protect against loss.
Currency and Exchange Rates: Currency detection and conversion are provided for convenience only. Exchange rates fluctuate constantly and may differ from the rates used in calculations. Always verify current exchange rates with your financial institution.
Updates and Changes: Interest rates, contribution limits, tax benefits, and other financial parameters are subject to change by government authorities, regulatory bodies, and financial institutions. We recommend verifying current rates and rules with official sources before making any decisions.
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By using this calculator, you acknowledge that you have read, understood, and agree to this disclaimer. You accept full responsibility for any decisions made based on the information provided by this tool.
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