Compound Interest Calculator
See how your money grows with the power of compounding — live results as you type
tuneAdjust Inputs
Maturity Amount
₹1,61,051
≈ 1.6 Lakh
Interest Earned
₹61,051
Growth: 61.1%
Principal
₹1,00,000
62.1% of maturity
Interest
₹61,051
37.9% of maturity
Time Period
5 yrs
Total duration
Eff. Annual Rate
10.38% EAR
Effective yield
Interest
37.9%
Principal
₹1,00,000
Interest
₹61,051
functions Compound Interest Formula
A = P × (1 + r/n)^(n×t)
P = Principal | r = Rate/100 | n = Compounding periods/year | t = Years
Live Result Illustration
Visual summary — updates instantly as you enter values above
Real-Life Guide to Using the Compound Interest
Power of compounding over time. Use the examples and checks below to turn the number into a practical decision.
When this calculator is useful
For understanding how any lump sum grows purely through compounding — outside a specific bank or mutual fund product — such as testing "what if I invested ₹2,00,000 at 9% for 6 years" for a school project, a loan comparison, or a general savings estimate.
For most people, the best way to use the Compound Interest is to try the real case first, then change one input at a time. That makes the trade-off visible. For example, with a loan calculator you can change tenure while keeping the same rate; with an investment calculator you can change return assumption while keeping the same monthly contribution; with a health, education or measurement calculator you can check how much one input changes the final category.
The result should answer a practical question: Can I afford this? How much should I save? Is this score enough? Is this measurement within range? What is the safer or cheaper option? If the output does not answer the decision clearly, adjust the inputs until the scenario matches your real situation.
lightbulb Real-Life Example
Six-year lump sum at 9%: Someone wants to see how ₹2,00,000 grows if left untouched for 6 years at an assumed 9% per annum, compounded annually.
1A = P(1+r)^n gives A = 2,00,000 × (1.09)^6 ≈ ₹3,35,420, so the compound interest earned is about ₹1,35,420 on the original ₹2,00,000 — more than 67% growth purely from compounding over 6 years.
2Now change one input, such as rate, time, quantity, unit or score, and compare the new result with the first one.
At a steady 9%, money left to compound roughly grows by two-thirds of its starting value within 6 years, which is why starting early matters more than the exact rate in many long-term plans.
Practical Advice
Use the Compound Interest as a planning tool, not just a number generator. Write down the inputs you used, because the final answer is meaningful only when you remember the assumptions behind it.
If the decision affects money, health, tax, safety, academics or legal compliance, keep a second check ready. That second check may be a bank quote, payslip, official rule, prescription, site measurement, mark sheet or invoice.
Common Mistakes
- Using the wrong compounding frequency for the scenario — entering "annual" for a product that actually compounds monthly or quarterly changes the maturity figure by a meaningful amount over long tenures.
- Confusing the compound interest earned with the total maturity amount — the calculator's "interest" output is only the gain, while "maturity value" includes the original principal added back.
- Assuming a higher compounding frequency always makes a dramatic difference — the gap between annual and monthly compounding at typical rates (7-9%) over a few years is usually a few thousand rupees, not a game-changing amount, unless the principal and tenure are both large.
- Applying a compound interest calculation to a loan EMI scenario, when loan repayments involve reducing principal balances each month and need an amortization calculation, not a straightforward compound growth formula.
- Not adjusting the rate for inflation when using this tool for long-term goal planning, so the nominal maturity value looks larger than what it will actually be worth in real purchasing power.
How to Interpret Results
The output splits into total interest earned and total maturity value — use total interest to see how much of the final amount is "new money" created purely by compounding versus your own original contribution.
A good interpretation looks at both the main result and the supporting values. If a page shows totals, ratios, categories, schedules or warnings, read those together instead of focusing only on the biggest number.
Compound Interest FAQs
Useful answers for interpreting the output, avoiding mistakes and using the result responsibly.
What is the exact compound interest formula used here?
A = P × (1 + r/n)^(n×t), where P is the principal, r is the annual interest rate as a decimal, n is the number of times interest compounds per year, and t is the time in years; compound interest earned is simply A minus P.
How is compound interest different from simple interest in practical terms?
Simple interest is calculated only on the original principal every period, so it grows in a straight line, while compound interest is calculated on the principal plus all previously accumulated interest, so it grows faster the longer the money is left invested.
Does compounding frequency (monthly vs annually) really make a big difference?
At typical rates over a few years the difference is modest — a few thousand rupees on a ₹2-5 lakh principal — but the gap widens with a higher principal, a higher rate, or a much longer tenure, so it is worth checking which frequency actually applies to your product.
Can I use this calculator for a real bank product like an FD?
Yes, the underlying formula is the same one used for FDs; just make sure to select the compounding frequency your bank actually uses (commonly quarterly for Indian FDs) to get a matching figure.
Why does the compound interest earned look small in the early years but large near the end?
Because each period's interest is calculated on a growing base that includes all prior interest, the rupee amount of interest earned accelerates over time even though the rate stays the same — this is the compounding effect becoming more visible as the base grows.
Is the interest amount shown here taxable?
Whether and how it is taxed depends on the actual instrument generating the interest (FD, bond, etc.) and your income slab; this calculator only computes the mathematical interest, not any tax treatment, so check the specific product's tax rules separately.
How do I use this to compare two different rates fairly?
Keep the principal, tenure, and compounding frequency identical between the two calculations and change only the rate, so the resulting difference in maturity value reflects purely the rate difference and nothing else.
What is the "Rule of 72" and does this calculator relate to it?
The Rule of 72 is a quick mental shortcut — dividing 72 by the interest rate gives an approximate number of years for money to double (e.g. at 9%, roughly 8 years) — and you can verify this approximation against the calculator's more precise year-by-year output.
Types of Compounding
The more frequently interest compounds, the higher your effective yield
📅
Annual
Interest added once per year. Simplest compounding method. Used in PPF, some bonds. Least powerful among compounding options.
PPF / Bonds
📆
Half-Yearly
Interest added twice per year. Common in some NSC, KVP, and bank deposits. Gives slightly better returns than annual compounding.
NSC / KVP
🔄
Quarterly
Interest added 4 times per year. Standard for most Indian bank FDs. The most common compounding frequency used in practice.
Most Common
📅
Monthly
Interest added 12 times per year. Used in some recurring deposits and savings accounts. Noticeably better than quarterly over long durations.
RD / Savings
⚡
Daily
Interest added 365 times per year. Used in US savings accounts and some liquid funds. Provides maximum compounding benefit among practical options.
Max Benefit
🔁
Continuous
Mathematical limit using e^rt. Used in financial modelling and theoretical finance. Marginally better than daily compounding — the theoretical ceiling.
Theoretical
8 Compounding Mistakes to Avoid
Small behavioural mistakes cost far more than market downturns — protect your compounding chain
1
Start Early
Ten years of compounding doubles money more than 30 years started late. The early decade's compounding is disproportionately powerful — time is the single most important variable in the compounding equation.
2
Don't Withdraw Interest
Withdrawing interest converts compound interest into simple interest. Let it compound fully — every rupee of interest withdrawn breaks the chain and dramatically reduces the final corpus over long periods.
3
Compare Effective Annual Rate (EAR)
A 12% annual rate compounded monthly equals a 12.68% EAR. Always compare the Effective Annual Rate — not the nominal rate — when evaluating two investments to ensure a like-for-like comparison.
4
Reinvest Dividends
Stock dividends not reinvested break the compounding chain entirely. Always use the Growth option in mutual funds rather than IDCW — reinvested dividends contribute significantly to long-term corpus through compounding.
5
Don't Ignore Inflation
A 7% nominal return with 6% inflation equals only 0.94% real return. Real compounding matters far more than nominal. Always calculate inflation-adjusted returns to understand your actual purchasing power growth.
6
Don't Break Long-Term Investments Early
Breaking at year 8 of a 15-year plan loses the steepest part of the compounding curve — the last few years give the most absolute rupee growth. Early exit destroys exponential gains that took years to build momentum.
7
Beware of Compound Interest on Debt
Credit card debt at 3%/month equals 42.58% EAR. Compounding works brutally against borrowers. Always pay off high-interest debt before investing — no investment safely beats 40%+ debt compounding.
8
Avoid High Expense Ratio Funds
A 2% expense ratio compounded over 20 years erodes approximately 33% of your corpus. Always choose low-cost index funds or ETFs — a 0.2% direct plan versus a 1.5% regular plan is a life-changing difference over decades.
Frequently Asked Questions
Everything you need to know about compound interest and how it builds wealth
What is compound interest and how is it different from simple interest?
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods — commonly called "interest on interest." Simple interest, by contrast, is calculated only on the original principal and grows linearly. Over long periods, compound interest grows exponentially while simple interest remains proportional. For example, ₹1 lakh at 12% for 10 years: compound interest (quarterly) gives ₹3.26 lakhs, while simple interest gives only ₹2.2 lakhs — a difference of over ₹1 lakh.
What is the Rule of 72 and how do I use it?
The Rule of 72 is a quick mental shortcut to estimate how many years it takes to double your money — simply divide 72 by the annual interest rate. At 12% compounding, your money doubles in 72 ÷ 12 = 6 years. At 6%, it takes 12 years. At 9%, approximately 8 years. The rule is surprisingly accurate for interest rates between 5% and 20% and is one of the most useful rules of thumb in personal finance for rapid mental calculations.
Why does the compounding frequency matter?
Higher compounding frequency means interest is added more often, so each subsequent calculation includes more accumulated interest. For ₹1 lakh at 10% over 10 years: annual gives ₹2,59,374; quarterly gives ₹2,68,506; monthly gives ₹2,70,704; and daily gives ₹2,71,791. The difference is modest at low principals but becomes significant at ₹10–50 lakh and 15–20 year tenures. Always check whether your FD or investment uses quarterly or monthly compounding.
What is Effective Annual Rate (EAR)?
The Effective Annual Rate (EAR) is the actual annual return you receive after accounting for compounding frequency within the year. It is calculated as EAR = (1 + r/n)^n − 1, where r is the nominal rate and n is the number of compounding periods. A 12% nominal rate compounded monthly gives an EAR of 12.68%. The EAR is the correct metric to compare two investments with different compounding frequencies — always compare EARs, never nominal rates.
How does compounding work in mutual funds?
Mutual fund NAVs (Net Asset Value) grow daily, which is equivalent to daily compounding of underlying returns. When you stay invested in a growth-option mutual fund, your entire corpus — including all previous gains — earns returns on the next day's growth. This is why switching to the IDCW (dividend) option breaks compounding: every dividend payout removes money from the compounding base. For long-term wealth, always choose the growth option in mutual funds.
Is FD interest compound or simple?
Bank FDs in India use compound interest, typically compounded quarterly. However, if you opt for interest payout (monthly or quarterly) instead of cumulative, it effectively becomes simple interest because the interest is removed before it can compound. For maximum benefit, always choose the cumulative FD option where interest compounds and is paid out only at maturity. Post Office deposits compound annually.
How does SIP use compounding?
A SIP (Systematic Investment Plan) harnesses compounding in two ways: each instalment earns returns that compound over its remaining tenure, and earlier instalments benefit from more years of compounding than later ones. While SIP is not technically "compound interest" in the traditional sense, the underlying mutual fund's daily NAV growth creates an equivalent compounding effect. The longer the SIP tenure, the more dramatically the earlier instalments compound — which is why the last few years of a long SIP produce the highest absolute rupee gains.
What is the best investment for compound interest in India?
For the highest compounding returns over 10+ years, equity mutual funds (SIP or lumpsum) with 12–15% historical CAGR are the best option despite market risk. For guaranteed compounding, PPF at 7.1% (annual compounding, tax-free) and bank FDs at 6.5–8% (quarterly compounding) are reliable. SSY offers 8.2% for a girl child. NPS compounds at approximately 9–12% with tax benefits. The "best" depends on your risk tolerance, tax bracket, and investment horizon.
How does inflation affect compound interest?
Inflation reduces your real (purchasing power-adjusted) returns significantly. If your investment earns 8% and inflation is 6%, your real return is approximately 1.89% — not 2%, due to the multiplicative nature of compounding. Over 20 years, ₹10 lakh at 8% nominal grows to ₹46.6L, but in today's purchasing power at 6% inflation, that's equivalent to only ₹14.5L. Always think in real returns, not nominal returns, when evaluating long-term wealth creation.
Can compound interest work against me?
Absolutely — compounding is brutally powerful on the debt side. Credit card debt at 3.5% per month compounds to 51.1% EAR. A personal loan at 18% p.a. compounding monthly gives 19.56% EAR. Missing EMIs triggers compound interest on outstanding dues. If you have credit card debt, compounding is actively destroying your wealth every month — the interest rate on debt almost always exceeds investment returns, making debt repayment the highest-return "investment" available.