Compound Interest Calculator
Calculate how your money grows with compound interest. See the total amount, interest earned, and year-by-year growth over time.
MATURITY AMOUNT
₹1.49 L
PRINCIPAL
₹1.00 L
TOTAL INTEREST
₹48,985
EFFECTIVE RATE
8.30%
Yearly Breakdown
| Year | Interest | Balance |
|---|---|---|
| 1 | ₹8,300 | ₹1.08 L |
| 2 | ₹17,289 | ₹1.17 L |
| 3 | ₹27,024 | ₹1.27 L |
| 4 | ₹37,567 | ₹1.38 L |
| 5 | ₹48,985 | ₹1.49 L |
How Compound Interest Works — The Complete Guide
Compound interest is the single most powerful concept in personal finance. Unlike simple interest — which earns returns only on your original principal — compound interest earns returns on both the principal and all previously accrued interest. This creates an accelerating snowball effect: the longer your money stays invested, the faster it grows.
The Compound Interest Formula
A = Final Amount | P = Principal | r = Annual rate (decimal) | n = Compounding periods/year | t = Time in years
Interest Earned = A − P
Example: ₹1,00,000 at 12% monthly (n=12) for 10 years → A = 1,00,000 × (1.01)^120 = ₹3,30,039. Interest earned = ₹2,30,039 — a 230% return on your principal!
How Compounding Frequency Impacts Returns (₹1 Lakh at 12% for 10 Years)
| Compounding Frequency | n Value | Final Amount | Interest Earned |
|---|---|---|---|
| Annually | 1 | ₹3,10,585 | ₹2,10,585 |
| Semi-Annually | 2 | ₹3,20,714 | ₹2,20,714 |
| Quarterly | 4 | ₹3,26,204 | ₹2,26,204 |
| Monthly | 12 | ₹3,30,039 | ₹2,30,039 |
| Daily | 365 | ₹3,31,946 | ₹2,31,946 |
In India, most Fixed Deposits compound quarterly. The difference between annual and daily compounding on ₹1 Lakh over 10 years is ₹21,000 — significantly more at scale. Equity mutual funds grow via daily NAV appreciation, effectively giving daily compounding.
The Power of Starting Early — Time Outperforms Capital
| Investor | Start Age | Monthly SIP | Total Invested | Corpus at Age 60 (12% p.a.) |
|---|---|---|---|---|
| Arjun (Early Start) | 25 | ₹5,000 | ₹21 Lakh | ₹1.76 Crore |
| Priya (10-Yr Delay) | 35 | ₹5,000 | ₹15 Lakh | ₹52 Lakh |
| Vikram (Later, More Capital) | 40 | ₹10,000 | ₹24 Lakh | ₹99 Lakh |
Arjun invests the least money in rupee terms, yet accumulates the most — 3.4× more than Priya and 1.8× more than Vikram who doubled the monthly amount. A 10-year head start is worth ₹1.24 Crore. Time is the most powerful input in any compound interest calculation.
Compound Interest vs. Simple Interest — The Diverging Paths
| Time Horizon | Simple Interest (12%) | Compound Interest (12% monthly) | Compounding Advantage |
|---|---|---|---|
| 5 years | ₹1,60,000 | ₹1,81,940 | +₹21,940 |
| 10 years | ₹2,20,000 | ₹3,30,039 | +₹1,10,039 |
| 20 years | ₹3,40,000 | ₹10,89,255 | +₹7,49,255 |
| 30 years | ₹4,60,000 | ₹35,94,964 | +₹31,34,964 |
Based on ₹1,00,000 initial investment at 12% per year. Simple interest grows linearly (same amount each year); compound interest grows exponentially (accelerating amount each year).
Common Indian Investment Products and Their Compounding
- Fixed Deposits (FDs): Compound quarterly. Current rates 7–8.5% for major banks. Ideal for capital preservation with guaranteed returns over 1–5 year horizons.
- PPF (Public Provident Fund): Compounds annually at 7.1% (2024–25 rate). Fully tax-exempt under the EEE (Exempt-Exempt-Exempt) regime; 15-year lock-in. Real return ~1–1.5% after 6% inflation.
- Equity Mutual Funds: Historical CAGR of 12–15% (Nifty 50 index, 20-year average). Growth through daily NAV increases. Best suited for 7+ year financial goals.
- ELSS (Tax-Saver) Funds: Equity funds with a mandatory 3-year lock-in. Historical returns 12–14%. Provides Section 80C tax deduction on investments up to ₹1.5 Lakh per year.
- NPS (National Pension System): Market-linked with 9–10% historical CAGR. Additional ₹50,000 deduction under Section 80CCD(1B) beyond the standard 80C limit.
The Rule of 72 — Estimate Doubling Time Instantly
A quick mental shortcut: Doubling Time ≈ 72 ÷ Annual Rate
- FD at 7%: 72 ÷ 7 = ~10.3 years to double your money
- Equity fund at 12%: 72 ÷ 12 = 6 years to double
- Savings account at 3.5%: 72 ÷ 3.5 = ~20.6 years to double
- Inflation at 6%: 72 ÷ 6 = 12 years for prices to double — meaning your idle cash loses half its purchasing power in 12 years
References
- SEBI Investor Education — sebi.gov.in/investor-education
- Reserve Bank of India Financial Literacy — rbi.org.in
- AMFI Mutual Fund Awareness Programme — amfiindia.com
- NISM Module 1: Compounding and Time Value of Money