What is compound interest and how does it work?

Compound interest is interest earned on both the initial principal and the accumulated interest from previous periods. Unlike simple interest which remains constant, compound interest grows exponentially over time because each interest payout starts earning interest itself.

What is the mathematical formula for compound interest?

The standard formula is: A = P × (1 + r / n)^(n × t), where A is the future maturity amount, P is initial principal, r is annual interest rate (as a decimal), n is number of compounding periods per year, and t is time period in years. Total Compound Interest = A − P.

How does compounding frequency affect total returns?

The more frequently interest is compounded (e.g. daily vs. monthly vs. annually), the higher the effective annual return. For example, ₹1 Lakh at 10% compounded annually yields ₹10,000, while compounded daily it yields approximately ₹10,515 due to rapid continuous reinvestment.

What is the Rule of 72 in compound interest?

The Rule of 72 is a quick mental math shortcut to estimate how many years it takes for your investment to double. Divide 72 by the annual interest rate: Years to Double ≈ 72 / Interest Rate. At 12% annual return, your money doubles in approximately 72 / 12 = 6 years.

What is the difference between Simple Interest and Compound Interest?

Simple interest is calculated only on the original principal throughout the entire loan or investment tenure. Compound interest is calculated on the principal plus all interest earned in previous periods, resulting in exponential wealth accumulation over long time horizons.

Compound Interest Calculator

Free online Compound Interest Calculator. Calculate future investment value, total interest earned, and effective annual rate (EAR) with year-by-year compounding schedules.

⚡ Interactive Calculation Engine Active

Please enable JavaScript in your browser to run live computations, 2D envelope diagrams, and export PDF reports.

How to Use Compound Interest Calculator

Enter the initial Principal Investment amount.
Input the Annual Nominal Interest Rate (%).
Specify the Investment Tenure in years or months.
Select the Compounding Frequency (Daily, Monthly, Quarterly, Semi-Annually, or Annually).
Optionally add recurring monthly or annual deposits to simulate disciplined savings.
Review the Future Maturity Value, Total Interest Earned, and year-by-year compounding growth chart.

The Power of Compounding Explained

Albert Einstein famously referred to compound interest as the "eighth wonder of the world". The key driver of compounding is time: during the early years, the growth appears modest, but as accumulated interest begins generating its own returns, the growth curve bends steeply upward. • **Principal (P)**: The baseline lump sum initially invested. • **Rate (r)**: The nominal annual interest rate offered. • **Compounding Frequency (n)**: 365 for daily, 12 for monthly, 4 for quarterly, 2 for semi-annual, 1 for annual. • **Tenure (t)**: Duration of investment in years.

Compounding Frequency Comparison (₹1,00,000 at 10% for 10 Years)

See how compounding frequency boosts final maturity value on a ₹1,00,000 deposit at 10% p.a. over 10 years: • **Annually (n = 1)**: Maturity Value = ₹2,59,374 | Total Interest = ₹1,59,374 • **Quarterly (n = 4)**: Maturity Value = ₹2,68,506 | Total Interest = ₹1,68,506 • **Monthly (n = 12)**: Maturity Value = ₹2,70,704 | Total Interest = ₹1,70,704 • **Daily (n = 365)**: Maturity Value = ₹2,71,791 | Total Interest = ₹1,71,791

Frequently Asked Questions

What is compound interest and how does it work?: Compound interest is interest earned on both the initial principal and the accumulated interest from previous periods. Unlike simple interest which remains constant, compound interest grows exponentially over time because each interest payout starts earning interest itself.
What is the mathematical formula for compound interest?: The standard formula is: A = P × (1 + r / n)^(n × t), where A is the future maturity amount, P is initial principal, r is annual interest rate (as a decimal), n is number of compounding periods per year, and t is time period in years. Total Compound Interest = A − P.
How does compounding frequency affect total returns?: The more frequently interest is compounded (e.g. daily vs. monthly vs. annually), the higher the effective annual return. For example, ₹1 Lakh at 10% compounded annually yields ₹10,000, while compounded daily it yields approximately ₹10,515 due to rapid continuous reinvestment.
What is the Rule of 72 in compound interest?: The Rule of 72 is a quick mental math shortcut to estimate how many years it takes for your investment to double. Divide 72 by the annual interest rate: Years to Double ≈ 72 / Interest Rate. At 12% annual return, your money doubles in approximately 72 / 12 = 6 years.
What is the difference between Simple Interest and Compound Interest?: Simple interest is calculated only on the original principal throughout the entire loan or investment tenure. Compound interest is calculated on the principal plus all interest earned in previous periods, resulting in exponential wealth accumulation over long time horizons.