Compound Interest Calculator India 2026
Calculate compound interest with 4 modes — Lump Sum, Recurring SIP, FD Comparison (SBI/HDFC/ICICI/PPF/NSC/SCSS rates), and Cost of Delay. Includes compounding frequency selector, year-by-year growth table, Rule of 72, CI vs SI comparison, and Section 80C tax guide.
What Is Compound Interest?
Compound interest (CI) is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which is calculated only on the original principal, compound interest creates exponential growth — often called the “snowball effect” of investing.
Albert Einstein reportedly called compound interest the “eighth wonder of the world — he who understands it, earns it; he who doesn’t, pays it.” Whether or not the quote is truly Einstein’s, the principle is universally powerful.
The key variables that determine compound interest growth:
- Principal (P) — the initial amount invested or deposited
- Interest Rate (r) — the annual rate of return (e.g., 7% for PPF, 6.5% for SBI FD)
- Compounding Frequency (n) — how often interest is compounded per year (quarterly for FDs, annually for PPF)
- Time Period (t) — the number of years the money stays invested
Compound Interest Formula
The standard formula to calculate compound interest is:
Where:
A = Maturity Amount (principal + interest)
P = Principal amount (initial investment)
r = Annual interest rate (as a decimal; 7% = 0.07)
n = Number of compounding periods per year (1=annual, 4=quarterly, 12=monthly, 365=daily)
t = Time period in years
Compound Interest = A − P
Worked Example — ₹1 Lakh FD at 7% for 5 Years
Let’s apply the formula with a common Indian Fixed Deposit scenario:
| Parameter | Value |
|---|---|
| Principal (P) | ₹1,00,000 |
| Rate (r) | 7% (0.07) |
| Compounding (n) | Quarterly (n = 4) |
| Time (t) | 5 years |
Compound Interest earned = ₹41,478
Compare this with simple interest: SI = 1,00,000 × 0.07 × 5 = ₹35,000. Compound interest earns ₹6,478 more (18.5% advantage) on the same deposit.
Compound Interest vs Simple Interest — Detailed Comparison
The gap between compound and simple interest widens dramatically with time and higher rates:
| Parameter | Simple Interest (SI) | Compound Interest (CI) |
|---|---|---|
| Formula | SI = P × r × t | CI = P(1 + r/n)nt − P |
| Interest on | Original principal only | Principal + accumulated interest |
| Growth pattern | Linear (straight line) | Exponential (accelerating curve) |
| ₹1L at 8% for 5 yrs | ₹1,40,000 | ₹1,46,933 (quarterly) |
| ₹1L at 8% for 10 yrs | ₹1,80,000 | ₹2,19,112 (quarterly) |
| ₹1L at 8% for 20 yrs | ₹2,60,000 | ₹4,80,102 (quarterly) |
| ₹1L at 8% for 30 yrs | ₹3,40,000 | ₹10,57,646 (quarterly) |
| Common usage | Rare (some personal loans) | FDs, PPF, RDs, SIPs, home loans |
Compounding Frequency — How It Affects Returns
Higher compounding frequency means interest is reinvested more often, giving slightly higher returns:
| Frequency | n | ₹1 Lakh at 7% for 10 yrs | Interest Earned | Extra vs Annual |
|---|---|---|---|---|
| Annually | 1 | ₹1,96,715 | ₹96,715 | — |
| Semi-Annually | 2 | ₹1,98,979 | ₹98,979 | +₹2,264 |
| Quarterly | 4 | ₹2,00,160 | ₹1,00,160 | +₹3,445 |
| Monthly | 12 | ₹2,00,966 | ₹1,00,966 | +₹4,251 |
| Daily | 365 | ₹2,01,375 | ₹1,01,375 | +₹4,660 |
The concept of Effective Annual Rate (EAR) accounts for this difference: at 7% stated rate with quarterly compounding, the EAR = (1 + 0.07/4)4 − 1 = 7.186%.
Rule of 72 — How Long to Double Your Money
The Rule of 72 is a quick mental formula: Years to Double = 72 ÷ Interest Rate.
| Interest Rate | Years to Double | India Investment |
|---|---|---|
| 6% | 12.0 years | Bank Savings Account |
| 7.1% | 10.1 years | PPF (current rate) |
| 7.5% | 9.6 years | KVP (Kisan Vikas Patra) |
| 7.7% | 9.4 years | NSC (National Savings Certificate) |
| 8% | 9.0 years | Good FD / SCSS |
| 10% | 7.2 years | Balanced Mutual Fund |
| 12% | 6.0 years | Equity Mutual Fund (avg) |
| 15% | 4.8 years | Small/Mid-Cap Fund (high risk) |
Rule of 114 — Years to triple = 114 ÷ rate (e.g., at 7% → 16.3 years)
Rule of 144 — Years to quadruple = 144 ÷ rate (e.g., at 8% → 18 years)
India FD Interest Rates — 2026 Comparison
Here are the current Fixed Deposit rates from major Indian banks as of Q1 FY 2025–26 (compounding quarterly):
| Bank / Scheme | 1 Year | 3 Year | 5 Year | Senior Citizen (5Y) |
|---|---|---|---|---|
| SBI | 6.80% | 6.75% | 6.50% | 7.00% |
| HDFC Bank | 6.60% | 7.00% | 7.00% | 7.50% |
| ICICI Bank | 6.70% | 7.00% | 7.00% | 7.50% |
| Axis Bank | 6.70% | 7.10% | 7.00% | 7.75% |
| Kotak Mahindra | 6.50% | 7.10% | 6.70% | 7.20% |
| Post Office TD | 6.90% | 7.10% | 7.50% | 7.50% |
Rates are indicative and subject to change. Check bank websites for the latest rates. Senior Citizen rates typically carry a 0.25–0.50% premium.
Government Schemes — Compounding Details
India’s sovereign-backed small savings schemes offer guaranteed compound interest returns:
| Scheme | Rate (FY26 Q1) | Compounding | Lock-in | Tax Status | 80C Eligible |
|---|---|---|---|---|---|
| Public Provident Fund (PPF) | 7.1% | Annually | 15 years | ✅ EEE (fully exempt) | ✅ Up to ₹1.5L |
| National Savings Certificate (NSC) | 7.7% | Annually | 5 years | Interest taxable | ✅ Up to ₹1.5L |
| Kisan Vikas Patra (KVP) | 7.5% | Annually | ~115 months | Interest taxable | ❌ |
| Senior Citizens Savings Scheme (SCSS) | 8.2% | Quarterly | 5 years | Interest taxable | ✅ Up to ₹1.5L |
| Sukanya Samriddhi Yojana (SSY) | 8.2% | Annually | 21 years (from a/c opening) | ✅ EEE (fully exempt) | ✅ Up to ₹1.5L |
| Post Office Time Deposit (5Y) | 7.5% | Quarterly | 5 years | Interest taxable | ✅ (5-year TD only) |
Tax Treatment of Compound Interest in India
Understanding the tax impact is critical because it significantly affects your real returns:
| Investment | Tax on Interest/Returns | TDS | Section 80C | After-Tax Return (30% slab) |
|---|---|---|---|---|
| Bank FD | Fully taxable at slab rate | 10% if interest > ₹40K | Only 5-year tax-saver FD | ~4.55% (on 6.5% FD) |
| PPF | 100% tax-free (EEE) | None | ✅ | 7.1% (full) |
| NSC | Annually taxable (accrued) | None | ✅ (including reinvested interest) | ~5.39% |
| SCSS | Fully taxable at slab rate | 10% if interest > ₹50K | ✅ | ~5.74% |
| Sukanya Samriddhi | 100% tax-free (EEE) | None | ✅ | 8.2% (full) |
| Equity Mutual Fund (LTCG) | 12.5% on gains > ₹1.25L/yr | None | Only ELSS | Varies |
The Cost of Delay — Why Starting Early Matters
The most powerful factor in compounding is time — not the amount invested or the rate of return. Here’s a real-world example:
| Scenario | Start at Age 25 | Start at Age 35 | Start at Age 45 |
|---|---|---|---|
| Monthly Investment | ₹5,000 | ₹5,000 | ₹5,000 |
| Expected Return | 12% p.a. | 12% p.a. | 12% p.a. |
| Years to Age 60 | 35 years | 25 years | 15 years |
| Total Invested | ₹21,00,000 | ₹15,00,000 | ₹9,00,000 |
| Corpus at 60 | ₹3.24 Cr | ₹94.88 L | ₹25.22 L |
| Interest Earned | ₹3.03 Cr | ₹79.88 L | ₹16.22 L |
Compound Interest for Recurring Deposits (RDs)
Recurring Deposits work differently from lump-sum FDs. With an RD, you make fixed monthly deposits and interest compounds quarterly:
- Compounding: Quarterly (like FDs)
- Each installment: Earns interest from the date of deposit to maturity
- First installment: Earns interest for the full tenure
- Last installment: Earns interest for only one month
- Tax: Interest is fully taxable at slab rate (TDS applies if > ₹40K/year, ₹50K for senior citizens)
For example, ₹5,000/month RD at 6.5% for 5 years: Total deposited = ₹3,00,000. Maturity = ~₹3,53,790. Interest = ~₹53,790.
Continuous Compounding — The Mathematical Limit
When compounding frequency approaches infinity (every instant), we get continuous compounding:
Where e = Euler’s number ≈ 2.71828
Example: ₹1 lakh at 7% for 10 years → A = 1,00,000 × e0.07×10 = 1,00,000 × 2.01375 = ₹2,01,375
The difference between daily compounding and continuous compounding is negligible (often less than ₹1 on ₹1 lakh over 10 years). This concept is mainly used in financial engineering and derivative pricing.
How Inflation Erodes Compound Interest Returns
When evaluating compound interest returns, always consider real returns (after inflation):
| Investment | Nominal Rate | After Tax (30% slab) | After Inflation (6%) | Real Return |
|---|---|---|---|---|
| Bank FD | 6.50% | 4.55% | −1.45% | Negative ❌ |
| PPF | 7.10% | 7.10% (EEE) | +1.10% | Positive ✅ |
| SCSS | 8.20% | 5.74% | −0.26% | Barely Zero ⚠️ |
| Sukanya Samriddhi | 8.20% | 8.20% (EEE) | +2.20% | Positive ✅ |
| Equity MF (avg LTCG) | 12.00% | ~10.50% | +4.50% | Strong ✅ |
How to Calculate Compound Interest in Excel / Google Sheets
Use these built-in functions for quick calculations:
=FV(rate/n, n*t, 0, -P)
Example: ₹1L, 7%, quarterly, 5 yrs → =FV(7%/4, 4*5, 0, -100000) = ₹1,41,478
=FV(rate/12, months, -monthly_payment, 0)
Example: ₹5,000/mo, 12%, 15 yrs → =FV(12%/12, 180, -5000, 0) = ₹25,22,447
=P*POWER(1+r/n, n*t)
Example: =100000*POWER(1+0.07/4, 4*5) = ₹1,41,478
For Compound Interest only (without principal): =FV(…) − P or =P*POWER(1+r/n, n*t) − P.
Common Mistakes in Compound Interest Calculations
- Confusing stated rate with effective rate — 7% compounded quarterly is actually 7.186% effective annual rate. Our calculator above shows both.
- Ignoring tax impact — FD interest is taxable, so a 6.5% FD gives only ~4.55% post-tax for the 30% slab. Always compare post-tax returns.
- Not adjusting for inflation — A 7% return with 6% inflation gives only 1% real growth. Use real return for long-term planning.
- Assuming constant rates — PPF and small savings rates are revised quarterly by the government. FD rates change with RBI repo rate.
- Withdrawing early — Breaking an FD before maturity usually attracts a 0.5–1% penalty, reducing your effective return.
- Comparing different compounding frequencies — A 7% quarterly FD vs 7.2% annual deposit: use the calculator above to see which gives higher maturity.
- Not considering the cost of delay — Even a 5-year delay can cost lakhs in lost compounding. Use our Cost of Delay mode above to see the impact.
Related Calculators & Tools
- SIP Calculator — Systematic Investment Plans use compounding through market-linked returns. Compare lump sum CI vs SIP returns.
- PPF Calculator — Calculate your PPF maturity with 7.1% annual compounding and tax-free EEE benefits.
- HLV Calculator — Human Life Value uses present value (reverse of compounding) to determine insurance cover.
- Home Loan EMI Calculator — Home loan EMI is derived using compound interest on the reducing balance. See how CI powers your EMI calculation.
- Car Loan EMI Calculator — Car loan interest also compounds — check your total interest outgo.
- Age Calculator — Calculate your exact age gap for cost-of-delay compounding analysis.