Free Interest Calculator
Online — 5 Modes

Interest Calculator — The Complete Guide to Every Type of Interest in India

Interest is the price of money — what you earn when you lend it, and what you pay when you borrow it. Yet most people in India estimate it, round it, or simply trust what the bank tells them. That trust can cost lakhs over a lifetime. This guide, paired with our free interest calculator online, gives you the exact numbers for every scenario — FD maturity, RD growth, loan cost, savings account earnings, PPF returns, and credit card penalties — in one place, in seconds.

We've built five calculation modes because interest is not one-size-fits-all. Simple interest works differently from compound interest. An FD compounds quarterly but a savings account compounds daily. A personal loan's "12% flat" rate is not the same 12% you see on a home loan. This guide explains every distinction, with real ₹ examples, so you can make genuinely informed financial decisions.

Simple Interest — The Foundation of All Financial Math

Simple interest (SI) is linear. Each period earns the same amount regardless of how much has already accumulated. It is the starting point for understanding all other interest types and the basis of several real financial products in India.

Where simple interest still rules in the real world:

• Flat-rate loans: Many two-wheeler financiers, consumer durable schemes, and some NBFCs advertise flat-rate interest — which is pure simple interest on the original principal throughout the loan.
• Short-term borrowing: Informal loans, post-dated cheque financing, and inter-corporate deposits often use daily or monthly simple interest.
• TDS late payment penalty: Section 201(1A) of the Income Tax Act charges 1% per month for late TDS deduction and 1.5% per month for late TDS deposit — calculated using simple interest by the exact number of days.
• Post Office Monthly Income Scheme (MIS): Monthly payouts are calculated on simple interest at 7.4% p.a., paid out monthly rather than compounded.

Calculating Interest by Days and Months

The need to calculate interest by days arises constantly — TDS penalties, credit card billing cycles, short-term loans, and bank overdraft interest all work on daily accrual. The formula adjusts cleanly: divide the annual rate by 365 to get the daily rate, then multiply by the number of days.

Example — TDS Late Payment Penalty:
TDS of ₹50,000 deposited 73 days late
Rate = 1.5% per month = 18% p.a.

Interest = 50,000 × 18 × (73 ÷ 365) ÷ 100
         = ₹1,800

Monthly calculation: 73 days spans 3 months (part of month counts as full month)
Under IT Act: 3 × 1.5% × 50,000 = ₹2,250 (statutory method)

→ Use Simple Interest mode, enter 73 days, rate 18% for the formula method.

For loan repayment timelines, switching to months is more intuitive. A ₹2 lakh personal loan at 15% p.a. for 18 months accumulates simple interest of ₹2,00,000 × 15 × (18/12) ÷ 100 = ₹45,000. Our tool handles all three units — days, months, years — with a single toggle.

Compound Interest — Where Real Wealth (and Real Debt) Gets Built

Compound interest fundamentally changes the mathematics of money. Interest is earned not just on principal but on every rupee of interest already accumulated. Over long periods, this creates exponential growth — the same force that makes FDs attractive for long-term savers and credit card debt catastrophic for those who carry a balance.

Same ₹1,00,000 at 7% p.a. for 5 years — four different outcomes:

Simple Interest:          ₹1,35,000   (interest = ₹35,000)
Annual compounding:       ₹1,40,255   (interest = ₹40,255)
Quarterly compounding:    ₹1,41,478   (interest = ₹41,478)  ← Indian FD standard
Monthly compounding:      ₹1,41,763   (interest = ₹41,763)
Daily compounding:        ₹1,41,906   (interest = ₹41,906)

Daily vs Simple Interest advantage: ₹6,906 extra on ₹1 lakh over 5 years

The difference between compounding frequencies narrows as you go higher — daily vs monthly is a small gap, but monthly vs annual is meaningful. The crucial leap is from simple interest to any form of compounding. That jump represents the power of earned interest earning its own return.

Effective Annual Rate — The True Rate to Compare

When comparing products that compound at different frequencies, the nominal rate is misleading. A 7% quarterly-compounded FD is not the same as a 7% annually-compounded PPF. The effective annual rate (EAR) standardises this:

EAR = (1 + R ÷ (n × 100))^n − 1

For 7% quarterly: EAR = (1.0175)^4 − 1 = 7.186% p.a.
For 7% monthly:  EAR = (1.00583)^12 − 1 = 7.229% p.a.

So a bank offering 7% monthly-compounded savings beats a 7.1% annual-compounded PPF on effective yield — worth knowing before you split your surplus.

Our compound interest calculator displays the Effective Annual Rate automatically alongside the maturity amount, so you can compare products fairly.

Fixed Deposit Interest Calculator — India's Safest Return, Calculated Precisely

Fixed deposits remain India's most widely held financial instrument, largely because they offer guaranteed returns, are covered by DICGC insurance up to ₹5 lakh, and are simple to open. But "simple" doesn't mean the math is straightforward — most people underestimate or overestimate their FD returns because they don't account for quarterly compounding correctly.

State Bank of India — Fixed Deposit Returns (2025)

SBI is the benchmark. Its rates for general investors: 6.80% for 1 year, 7.00% for 2 years, 6.75% for 3 years, and 6.50% for 5 years. Senior citizens receive an additional 0.50%.

₹5,00,000 SBI FD — 2 years at 7.00% (quarterly compounding)

Maturity = 5,00,000 × (1 + 7/400)^(4×2)
         = 5,00,000 × (1.0175)^8
         = 5,00,000 × 1.14868
         = ₹5,74,341

Interest Earned = ₹74,341
Monthly equivalent = ₹3,097/month passive income

HDFC Bank — FD Rates and Monthly Payout Option

HDFC Bank offers 7.10% for 1 year and 7.25% for the 15–21 month bucket, making it slightly more competitive than SBI for short-duration deposits. HDFC also offers a monthly interest payout FD, where interest is credited to your account each month at a slightly lower effective rate (because the bank doesn't benefit from reinvesting your quarterly interest). Our fixed deposit calculator handles both cumulative and monthly-payout modes — simply switch to monthly compounding frequency to model the payout version.

ICICI Bank and Axis Bank

ICICI Bank and Axis Bank offer nearly identical rates to HDFC — 7.10% to 7.25% for tenures between 1 and 2 years. Axis Bank's 7.20% for the 1-year tenure gives it a marginal edge for short-term parking. The key differentiator between these banks is usually the special tenure "sweet spots" — ICICI's 15-month and Axis's 13-month buckets often carry peak rates not available at round-number tenures.

PNB and Public Sector Banks

Punjab National Bank (PNB) offers 6.80% for 1 year, stepping down to 6.50% for 5 years. Its senior citizen scheme adds 0.50%, making PNB 5-year FD effectively 7.00% for retirees. For those who specifically need a PNB fixed deposit maturity calculation, enter 6.80% in our FD mode with quarterly compounding for an exact figure matching PNB's official calculator.

Post Office Time Deposit — Underrated and Government-Backed

Post Office Time Deposits are among India's most overlooked fixed-income instruments. Rates in 2025: 6.90% (1 yr), 7.00% (2 yr), 7.10% (3 yr), and 7.50% (5 yr). The 5-year Post Office TD is sovereign-backed, Section 80C eligible, and yields more than most bank FDs at the same tenure. Monthly interest for the 5-year TD is credited to your Post Office savings account, effectively giving you the best rate with liquidity. Use the Post Office 5-year rate of 7.50% in our FD calculator to see your maturity amount — the result consistently beats comparable bank products.

Recurring Deposit — Systematic Saving with Guaranteed Returns

A Recurring Deposit is effectively a fixed deposit built in monthly instalments. You deposit a fixed sum each month — as low as ₹100 — for a chosen tenure, and at maturity you receive the accumulated principal plus compounded interest. Banks use quarterly compounding on each instalment separately, which makes the RD maturity formula slightly more complex than a standard FD calculation.

RD Maturity =  Σ (Monthly Deposit × (1 + R/400)^(4 × remaining_months/12))
              for each instalment from month 1 to month n

SBI RD Example: ₹5,000/month | 6.50% p.a. | 24 months
Total Deposited: ₹1,20,000
Maturity:        ≈ ₹1,28,535
Interest Earned: ≈ ₹8,535
Effective return: 7.1% on average deployed capital

For reference across major banks in 2025: SBI offers 6.50% on 1–2 year RDs; ICICI Bank and Axis Bank offer 7.10% for similar tenures, making them meaningfully better for recurring deposits. Post Office RD comes in at 6.70% — competitive and backed by the sovereign guarantee that bank FDs only approximate through DICGC insurance.

One often-missed point: the effective return on an RD is always lower than the stated rate because early instalments earn the full interest while later ones earn very little. A 24-month RD at 6.5% has an effective yield closer to 3.5% on your total deposits (since on average each rupee is deployed for only half the total tenure). This does not make RDs bad — it makes them the right tool for building a corpus from regular income, not for deploying a lump sum.

Loan Interest — The Number That Determines Your True Cost of Borrowing

Loan interest is where the stakes are highest — and where financial institutions' marketing creates the most confusion. The single most important skill in personal finance is understanding exactly how much interest you will pay over the life of a loan, not just the monthly EMI. Our loan interest calculator makes this transparent for every loan type, using either flat rate or reducing balance method.

The Flat Rate Illusion

Many consumer loan products — particularly two-wheeler loans, consumer durable EMIs, and some NBFC personal loans — advertise flat interest rates. Flat rate means interest is charged on the original principal for the entire loan duration, even as you repay. This sounds straightforward, but it means a "10% flat" loan is actually far more expensive than a 10% reducing balance loan.

₹1,00,000 loan, 10% p.a., 2 years — Flat Rate vs Reducing Balance:

FLAT RATE (Simple Interest):
Total Interest = 1,00,000 × 10 × 2 ÷ 100 = ₹20,000
Monthly EMI   = (1,00,000 + 20,000) ÷ 24 = ₹5,000
Effective reducing-rate equivalent: ≈ 18.0% p.a.

REDUCING BALANCE:
Monthly EMI = ₹4,615 (at true 10% reducing)
Total Interest = ₹10,767
You save ₹9,233 just by choosing reducing balance at the same stated rate.

Rule of thumb: Flat rate × 1.8 ≈ equivalent reducing rate

Always ask your lender whether the rate quoted is flat or reducing. For all home loans and car loans from scheduled commercial banks, RBI mandates the use of reducing balance (diminishing balance) method. The flat rate trap is most common in dealership finance and NBFC consumer loans.

Home Loan — The Largest Interest Calculation of Most Lives

Home loans are the longest and largest loans most Indians take. At current rates of 8.50%–9.25% p.a. (reducing balance), the total interest on a ₹50 lakh home loan over 20 years is larger than the principal itself:

₹50,00,000 home loan | 8.75% p.a. | 20 years (reducing balance):

Monthly EMI        = ₹44,115
Total Paid         = ₹1,05,87,600
Total Interest     = ₹55,87,600 (111% of principal!)
Interest in Year 1 = ₹4,33,219  (principal repaid just ₹95,561)
Interest in Year 10 = ₹3,71,542 (principal repaid ₹1,57,238 — finally accelerating)

The early years of a home loan are overwhelmingly interest — this is why prepayment in the first five years saves dramatically more than prepayment in year 15. Our loan calculator shows the year-by-year split of principal and interest so you can see exactly when your repayments start making a real dent in the outstanding balance.

Car Loan, Two-Wheeler Loan, and Auto Finance

Vehicle loans — whether for a car, bike, or commercial vehicle — typically run for 3–7 years at 8.75%–11% p.a. on reducing balance through banks, or at flat rates through manufacturer finance arms. For a ₹8 lakh car loan at 9.25% over 5 years, total interest on reducing balance is approximately ₹2.08 lakh — equivalent to paying for nearly 26% of the car in interest alone.

Two-wheeler loans are where the flat rate trap is most prevalent. A 2-wheeler loan advertised at "10% flat" over 3 years costs roughly ₹30,000 in interest on ₹1 lakh borrowed — the equivalent of a 18% reducing balance rate. Our calculator makes this transparent: model both rates and compare the total interest, not just the EMI.

Personal Loan, Gold Loan, and Education Loan

Personal loans carry the highest interest rates in the retail lending space — typically 10.75% to 18% p.a. on reducing balance from banks, and up to 24% from NBFCs and fintech lenders. On a ₹5 lakh personal loan at 14% for 3 years, you pay approximately ₹1.13 lakh in total interest — 22.6% on top of what you borrowed.

Gold loans offer a lower-cost alternative when you have pledgeable gold assets. Rates from banks start at 9.5% p.a. (reducing), while Muthoot and Manappuram charge 12%–24% depending on the product and LTV. For education loans (also called study loans), government banks like SBI and Bank of Baroda offer rates starting at 8.50% p.a. with a moratorium period (no repayment during the course plus 1 year), after which the full EMI begins.

PPF — India's Best Long-Term Compounding Product (And It's Tax-Free)

The Public Provident Fund earns 7.1% per annum with annual compounding and holds a unique EEE (Exempt-Exempt-Exempt) tax status — investment deductible under Section 80C, annual interest tax-free, and maturity amount fully exempt from tax. No other mainstream investment in India combines sovereign safety, reasonable returns, and complete tax exemption.

PPF at ₹1,50,000/year for 15 years at 7.1% (annual compounding):

Year 1 investment:  Grows to 1,50,000 × (1.071)^15 = ₹4,40,355
Year 15 investment: Grows to 1,50,000 × (1.071)^1  = ₹1,60,650

Total Deposited:    ₹22,50,000
Maturity Amount:    ≈ ₹40,68,209
Tax-Free Gain:      ₹18,18,209 — every rupee of which is yours to keep

The 15-year lock-in is PPF's main drawback, though partial withdrawals are permitted from Year 7. For anyone in the 30% tax bracket, PPF's 7.1% tax-free return is equivalent to a pre-tax return of approximately 10.14% — which outperforms most debt mutual funds on an after-tax basis. Use our Simple Interest mode set to annual compounding, 7.1%, and 15 years to model your exact PPF maturity.

Savings Account Interest — More Complex Than It Appears

Savings account interest is calculated daily on the closing balance and credited to your account monthly (for most banks) or quarterly. The formula is simple, the execution is not — your balance changes daily, so each day's interest is fractionally different.

Daily interest accrual (daily balance method):
Day's Interest = (Account Balance × Annual Rate) ÷ 365

Example: ₹2,00,000 balance at 3.00% p.a. for 30 days:
Monthly credit = 2,00,000 × 3.00 ÷ 365 × 30 = ₹493

Current savings account rates in India (2025):
SBI: 2.70% p.a.       | HDFC Bank: 3.00%    | ICICI Bank: 3.00%
Axis Bank: 3.00%      | Kotak 811: 3.50%    | Post Office SB: 4.00%
Small Finance Banks: Up to 7.50% (Au Small Finance, ESAF, Suryoday)

The gap between SBI's 2.70% and a small finance bank's 7.50% on the same ₹5 lakh balance is ₹23,500/year — a significant passive income differential for surplus funds. Small finance bank deposits are covered by DICGC insurance up to ₹5 lakh, making them as safe as regular bank deposits for amounts within that limit.

Credit Card Interest — India's Most Expensive Borrowing

Credit card interest in India is among the most expensive money available to consumers — typically 2.5% to 3.5% per month (30% to 42% annually). Cards use daily compounding on the outstanding balance from the transaction date once you carry a balance beyond the due date.

Understanding Credit Card APR:

Outstanding balance: ₹50,000
Monthly rate: 3.0% (APR = 36%)
If you pay only the minimum (5% = ₹2,500/month):

Month 1: ₹50,000 + ₹1,500 interest − ₹2,500 payment = ₹49,000
Month 2: ₹49,000 + ₹1,470 interest − ₹2,450 payment = ₹48,020
...
Time to full repayment: Over 5 years
Total Interest Paid: ₹47,850 — nearly equal to the original balance!

The minimum payment trap is real. Carrying ₹1 lakh on a credit card at 3%/month costs ₹36,000 in annual interest — guaranteed, regardless of market conditions. Compare this to the 7%–8% FD returns you're earning on any savings, and the first financial priority for anyone with card debt is repayment, not investment.

How to Compare Interest Rates Fairly — Per Annum, Monthly, and Daily Rates

Different financial products quote rates differently, and direct comparison is usually misleading:

• Per annum (p.a.): The standard quoted rate for FDs, home loans, personal loans, and savings accounts. Always ask if this is a flat or reducing rate for loans.
• Monthly rate: Credit cards and some loan products quote monthly rates. Multiply by 12 to get the annual rate — but note that monthly compounding makes the effective annual rate slightly higher: 3%/month = 42.6% EAR, not 36%.
• Daily rate: Used for savings account accrual, credit card interest, and overdraft facilities. Divide the annual rate by 365.

The only fair comparison across all products is the Effective Annual Rate (EAR) — which our compound interest calculator displays automatically. An 8% home loan (reducing, monthly compounding) has an EAR of 8.30%. A 7.50% Post Office TD (quarterly compounding) has an EAR of 7.71%. The second product actually earns more in real terms despite the lower nominal rate.

Common Mistakes That Cost Indian Investors Lakhs

• Confusing flat and reducing rates: The most expensive financial mistake in lending. Always convert flat rates before comparing.
• Ignoring compounding frequency: Two FDs at the same rate but different compounding schedules return different amounts. Quarterly always beats annual.
• Missing the tenure sweet spots: Banks often offer peak rates at specific tenures (e.g., 444 days, 555 days). Calculate the actual maturity before locking in at a round-number tenure.
• Underestimating credit card cost: The effective annual cost of rolling credit card debt (36%–42%) makes it impossible to invest your way out — repay first.
• Treating PPF as just a tax-saving instrument: PPF's EEE status and 15-year compounding at 7.1% makes it one of the best wealth-building instruments in India, not just a last-minute tax box to tick.

For authoritative and up-to-date bank rate information, refer directly to the Reserve Bank of India website and individual bank websites. For a comprehensive FD rate comparison across banks, BankBazaar and the AMFI India portal are reliable starting points.