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Compound Interest Calculator

Calculate compound interest with multiple compounding frequencies. See exactly how your money grows year by year — free, no signup required.

Compound Interest
Total Amount
₹1,40,122
Principal Amount
₹1,00,000
Total Interest
₹40,122

What is Compound Interest?

Compound interest is the interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which is calculated only on the principal, compound interest causes your money to grow exponentially over time. This is why it is often called the "eighth wonder of the world" — a phrase attributed to Albert Einstein.

When you invest money at compound interest, the interest you earn each period is added to your principal, and the next period's interest is calculated on this larger amount. This snowball effect accelerates growth significantly, especially over long time horizons.

Compound Interest Formula

The compound interest formula is:

A = P × (1 + r / (n × 100))^(n × t)

Where:
A = Final amount (principal + interest)
P = Principal amount (initial investment)
r = Annual interest rate (in percentage)
n = Number of compounding periods per year
t = Time in years

Interest Earned = A − P

For example, if you invest ₹1,00,000 at 7% p.a. compounded monthly for 5 years: A = 1,00,000 × (1 + 7 / (12 × 100))^(12 × 5) = ₹1,41,763 (approx.)

How to Use This Calculator

  1. Enter the Principal Amount — This is the initial amount you are investing or depositing. Use the slider or type directly into the input box.
  2. Set the Interest Rate — Enter the annual interest rate offered by your bank, FD, or investment product (in % per annum).
  3. Choose the Time Period — Select how many years you plan to keep the investment. Longer durations amplify compound growth significantly.
  4. Select Compounding Frequency — Choose how often interest is compounded: Yearly, Half-Yearly, Quarterly, or Monthly. More frequent compounding leads to higher returns.
  5. Read the Results — The calculator instantly shows your Total Amount, Principal, and Total Interest Earned. The chart and year-by-year table give a full breakdown.

Compound Interest vs Simple Interest

The key difference between compound and simple interest lies in how interest is calculated each period:

  • Simple Interest — Calculated only on the original principal. Formula: SI = (P × r × t) / 100. Interest earned is the same every year.
  • Compound Interest — Calculated on principal plus accumulated interest. The interest amount grows every year as the base increases.
  • Growth rate — Compound interest grows exponentially while simple interest grows linearly.
  • Long-term impact — Over 10–30 years, compound interest can result in returns that are 2x–5x more than simple interest at the same rate.
  • Example — ₹1,00,000 at 10% for 20 years: Simple Interest gives ₹3,00,000 total; Compound Interest (monthly) gives ₹7,32,816 total — more than double.

Power of Compounding

Time is the most critical factor in compounding. The longer you stay invested, the more powerful the compounding effect becomes. This is why financial advisors always stress starting early.

  • Start at 25 vs 35 — Investing ₹5,000/month from age 25 vs age 35 (both at 10% p.a.) results in nearly 2.5x more wealth at 60, even though the 25-year-old only invested 10 extra years.
  • Reinvestment matters — Every rupee of interest you leave invested earns more interest. Withdrawing interest prematurely kills compounding.
  • Rule of 72 — Divide 72 by the annual interest rate to find how many years it takes to double your money. At 8%, your money doubles in 9 years (72 ÷ 8 = 9).
  • Frequency effect — Monthly compounding at 12% grows ₹1 lakh to ₹3.30 lakh in 10 years; yearly compounding at the same rate gives ₹3.10 lakh. The gap widens over time.

Advantages of Compound Interest

  • Exponential growth — Unlike linear simple interest growth, compounding creates an accelerating snowball of wealth.
  • Passive wealth creation — You earn interest on interest without any additional effort or investment.
  • Inflation protection — Instruments offering compound interest (FDs, bonds, mutual funds) often outpace inflation over the long term.
  • Flexibility — Choose compounding frequency to match your financial goals: monthly compounding suits short-term goals, while yearly suits long-term plans.
  • Widely available — Compound interest is available in fixed deposits, recurring deposits, savings accounts, PPF, NPS, and most mutual funds.
  • Predictable returns — For fixed-rate instruments, you can calculate exactly how much you will earn using this calculator.

Frequently Asked Questions

Simple interest is calculated only on the principal amount throughout the entire duration. The formula is SI = (P × r × t) / 100. In contrast, compound interest is calculated on the principal plus any interest already accumulated. This means each compounding period, your effective principal grows, resulting in exponentially larger returns. For example, ₹1,00,000 at 10% for 10 years earns ₹1,00,000 in simple interest but ₹1,59,374 in compound interest (monthly compounding) — a difference of nearly ₹60,000.
The more frequently interest is compounded, the higher the effective annual yield. This is because interest is added to the principal more often, giving the newly added interest less time to wait before it too starts earning returns. For a ₹1,00,000 investment at 10% for 5 years: Yearly compounding gives ₹1,61,051; Half-yearly gives ₹1,62,889; Quarterly gives ₹1,63,862; Monthly gives ₹1,64,533. The difference between yearly and monthly compounding is ₹3,482 — and this gap widens significantly over longer periods.
The Rule of 72 is a quick mental math shortcut to estimate how long it takes to double your money at a given interest rate. Simply divide 72 by the annual interest rate. For example: at 6% p.a., your money doubles in 72 ÷ 6 = 12 years. At 9% p.a., it doubles in 8 years. At 12% p.a., it doubles in 6 years. This rule works best for interest rates between 6% and 20% and assumes compound interest. It is a useful tool for quickly comparing investment options without needing a calculator.
Yes — compound interest is a double-edged sword. When you are borrowing money (credit cards, personal loans, home loans), compound interest works against you in the same way it works for you when investing. Interest on unpaid balances accumulates on top of itself, causing debt to snowball rapidly. For example, a credit card with a 36% p.a. interest rate (3% monthly) on an unpaid ₹50,000 balance will grow to ₹73,382 in just one year if no payments are made. This is why financial advisors always recommend paying off high-interest debt before investing.
Several popular investment options in India offer compound interest: Fixed Deposits (FDs) with quarterly or monthly compounding; Recurring Deposits (RDs) with quarterly compounding; Public Provident Fund (PPF) with annual compounding at government-set rates; National Savings Certificate (NSC) with annual compounding; National Pension System (NPS) through market-linked compounding; Mutual Funds where returns are reinvested and compound over time; and savings accounts where interest is credited quarterly. For the highest compounding benefit, look for instruments that compound monthly or quarterly and reinvest returns rather than paying them out.