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CISI

Compound Interest

A = P(1 + r/n)^nt with full breakdown

Quick Answer — Compound Interest

Investing ₹1 Lakh at 8% compounded quarterly for 5 years yields ₹1,48,595 — that's ₹48,595 in interest. Compound interest earns "interest on interest," making it far more powerful than simple interest over time.

Standard Formula Updated 2026
₹
₹1,00,000
₹10,000₹2,00,00,000
%
8%
1%30%
years
5years
1years40years
Methodology
Free forever Data stays on your device Works offline (PWA) Verified formulas

Maintained by: Sagar Sahni, Calc Labz  |  Review: formula checks, worked examples, and periodic updates

Use with care: Finance and tax outputs are planning estimates only and should be checked against current rules.

Need a correction? Contact us with the calculator name and the issue you found.

Formula & Worked Example

The math behind the Compound Interest

Mathematical Formula

A = P \cdot \left(1 + \frac{r}{n}\right)^{nt}
Where: - **A** is the final maturity amount. - **P** is the principal balance. - **r** is the annual interest rate (decimal). - **n** is the number of times interest compounds per year. - **t** is the time in years.

Step-by-Step Worked Example

Suppose you invest **₹1,00,000** at **8%** interest compounded quarterly (n = 4) for **5 years**. - A = 1,00,000 × (1 + 0.08 / 4)^(4 × 5) - A = 1,00,000 × (1.02)^20 - **A ≈ ₹1,48,595** (Interest earned: **₹48,595**)

Frequently Asked Questions

Common questions about the Compound Interest

What is compound interest and how does it differ from simple interest?
Compound interest is calculated on both the initial principal and the accumulated interest from previous periods ("interest on interest"). Simple interest is only calculated on the original principal. Over time, compound interest grows exponentially while simple interest grows linearly.
How does compounding frequency affect returns?
More frequent compounding generates slightly higher returns. Annual compounding < Half-yearly < Quarterly < Monthly < Daily. For example, ₹1 Lakh at 8% for 5 years yields: ₹1,46,933 (annual) vs ₹1,48,595 (quarterly) vs ₹1,48,985 (monthly). The difference is marginal for short tenures.
What is the Rule of 72?
The Rule of 72 is a quick mental math shortcut: divide 72 by the annual interest rate to estimate how many years it takes to double your money. At 8% return, money doubles in 72/8 = 9 years. At 12%, it doubles in 72/12 = 6 years.
Does compound interest work on all investments?
Compound interest applies to bank FDs, PPF, mutual funds (when returns are reinvested), bonds, and savings accounts. Stocks grow through price appreciation and dividend reinvestment, which produces a similar compounding effect. Plain savings accounts may use simple interest.
How much can ₹1 Lakh grow in 20 years?
At 8% compound interest (quarterly): ~₹4.88 Lakh. At 12%: ~₹9.65 Lakh. At 15%: ~₹16.37 Lakh. The key takeaway: even small differences in return rates create huge differences over long periods due to the exponential nature of compounding.

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What is the Compound Interest?

The Compound Interest Calculator shows how your money grows with the power of compounding — earning interest on interest. Unlike simple interest, compound interest accelerates wealth creation exponentially over time. Our calculator supports multiple compounding frequencies: monthly, quarterly, half-yearly, and annually.

How to Use the Compound Interest

  1. Enter Principal: Enter your principal in Indian Rupees (₹) in the input field. The calculator will validate your input automatically.
  2. Enter Interest Rate: Enter your interest rate (in %) in the input field. The calculator will validate your input automatically.
  3. Enter Time Period: Enter your time period (in years) in the input field. The calculator will validate your input automatically.
  4. View Your Results: The Compound Interest displays your results instantly in the output panel. You will see the primary result along with a detailed breakdown of secondary outputs. Scroll down for charts, interpretations, and expert advice.

Key Features

  • Instant Compound Interest calculations with real-time updates
  • No signup, no registration — 100% free forever
  • All calculations happen in your browser — zero data sent to servers
  • Works offline as a Progressive Web App (PWA)
  • Mobile-friendly responsive design
  • Verified financial formulas updated for 2026

Why Use Calc Labz Compound Interest?

The Calc Labz Compound Interest stands out because it combines accuracy with simplicity. Unlike other online calculators, we provide detailed breakdowns, step-by-step formulas, and actionable advice alongside your results. Our financial calculators are regularly updated to reflect current rates, rules, and standards for India (2026). Whether you are a student, professional, or just need a quick calculation — Calc Labz delivers reliable results instantly.

Key Terms & Glossary

Principal
The original amount of money borrowed or invested, before any interest is applied.
Interest Rate
The percentage charged on borrowed money or earned on invested money, usually expressed per annum.
Compound Interest
Interest calculated on both the initial principal and previously accumulated interest — "interest on interest."
Amortization
The process of spreading loan repayment into equal installments over a fixed period.
Maturity
The date on which a financial instrument (FD, bond, PPF) reaches its full term and the principal is returned.
CAGR
Compound Annual Growth Rate — the smoothed annual rate of return on an investment over a specified period.