Simple interest calculator
What does simple interest come to, and what does it cost against compounding?
₹4,00,000interest over 10 years
- You get back
- ₹9,00,000
- Compounded it would be
- ₹10,79,462
- What simple interest costs you
- ₹1,79,462
Simple interest never earns on its own interest, so the two bars separate slowly and then all at once. Most Indian deposits compound quarterly — the compound interest calculator models those.
- Simple
- Compounded
| Year | Simple | Compounded | Gap |
|---|---|---|---|
| 1 | ₹5,40,000 | ₹5,40,000 | ₹0 |
| 2 | ₹5,80,000 | ₹5,83,200 | ₹3,200 |
| 3 | ₹6,20,000 | ₹6,29,856 | ₹9,856 |
| 4 | ₹6,60,000 | ₹6,80,244 | ₹20,244 |
| 5 | ₹7,00,000 | ₹7,34,664 | ₹34,664 |
| 6 | ₹7,40,000 | ₹7,93,437 | ₹53,437 |
| 7 | ₹7,80,000 | ₹8,56,912 | ₹76,912 |
| 8 | ₹8,20,000 | ₹9,25,465 | ₹1,05,465 |
| 9 | ₹8,60,000 | ₹9,99,502 | ₹1,39,502 |
| 10 | ₹9,00,000 | ₹10,79,462 | ₹1,79,462 |
Simple interest is the version that stops growing. The interest is worked out on the amount you started with and never on the interest already earned, so ten years of it is just year one repeated ten times. That makes it the right maths for a hand loan to a relative, a builder's instalment plan or a flat-rate vehicle quote — and the wrong maths for a deposit, which is why the second figure above shows what the same money would have done had the interest been allowed to earn too.
A worked example
A cousin borrows ₹2,00,000 to bridge a house purchase and you agree on 12% a year, simple, repaid in one go after 3 years. Put those three numbers in above and the interest comes to ₹72,000 — ₹24,000 a year, the same every year — so ₹2,72,000 comes back.
Had that money been compounded annually at the same 12% it would have grown to ₹2,80,986, or ₹80,986 of interest. The gap is ₹8,986: small, because the two are identical at the end of year one and only part from year two. Push the same loan out to five years and the gap is ₹32,468; leave it for ten and the gap is ₹1,81,170 — more than a third of the ₹4,21,170 that compounding would have paid. Simple interest is cheap over a year and expensive over a decade.
| Simple interest | Compounding | |
|---|---|---|
| Interest is charged on | The original amount, always | The amount plus interest so far |
| Where you meet it | Hand loans between family, builder instalment plans, flat-rate vehicle and consumer-durable quotes, gold-loan interest on the sanctioned sum, overdue-payment clauses | Bank FDs and RDs, savings accounts, PPF and EPF, mutual funds, every EMI loan |
| Effect of a long tenure | None — each year is identical | Compounds; the later years do the work |
| Good news for | The borrower, on a genuine lump-sum loan | The saver |
The second figure above uses annual compounding, the gentlest kind. Most Indian deposits compound quarterly, so against a real FD the gap is wider still.
What this number leaves out
Any fee
Processing and documentation charges, a lender-bundled insurance premium, stamp duty on the loan agreement — real money, none of it interest.
Tax
The interest is taxable at your slab, and a bank or company paying it deducts TDS under section 194A. What you keep is less than what is shown.
Whole years only
Real deposits and real loans count days. This works in full years, so a loan running 3 years and 4 months needs the time entered as a fraction.
Nothing going wrong
No part-payment, no penal interest on a missed date, no default, and no inflation — ₹2,72,000 three years out buys less than it does today.
Two more things the result cannot know. It assumes the rate holds for the whole term, which a written agreement should say in as many words; and it assumes the interest is actually paid, which between family is the failure mode far more often than the arithmetic is. And if the quote you are checking is a flat-rate loan rather than a lump-sum one, this page tells you the rupees of interest but not the true rate you are paying — that comparison belongs to the EMI calculator.
Next, most people want the compound interest calculator to see what the same money does when the interest is allowed to earn, the FD calculator to price the quarterly-compounded version a bank will actually sell you, or the personal loan calculator if the number you are checking is one somebody is charging you.
What is the formula for simple interest?
Interest = Principal × Rate × Time ÷ 100, with the rate as a yearly percentage and the time in years. Add the interest back to the principal for the amount you get or owe at the end. For a part-year, use the fraction: nine months is 0.75 years, 146 days is 0.4 of a year. There is nothing else in it — no compounding step, no frequency to choose.
Is a loan quoted at simple interest cheaper than one on reducing balance?
Usually the opposite, and this is the single most expensive misreading of the word "simple". A flat or simple-interest loan charges the whole original amount for the whole tenure even though your EMIs are shrinking the balance every month, so by the last year you are paying interest on money you repaid long ago. A reducing-balance loan charges only what is still outstanding. As a rough rule the effective reducing-balance cost of a flat quote is close to double the number advertised, so 12% flat is not competing with 12% on an EMI — check it against the EMI calculator before you sign.
Do banks pay simple interest on a fixed deposit?
No. Bank fixed deposits and recurring deposits compound, conventionally every quarter, and savings accounts credit interest quarterly on daily balances. Simple interest turns up in a bank only in narrow places — some short-tenure or pay-out-monthly deposits where the interest leaves the account instead of staying to earn, and overdue-interest clauses. If you are pricing a deposit, the compound interest calculator is the one that matches the passbook.
Do I pay tax on simple interest I earn?
Yes. Interest is taxable at your slab rate — as "income from other sources" if it came from a private loan, with no exemption for the fact that no bank was involved. Where a bank or company pays it, TDS is deducted under section 194A of the Income Tax Act once the year's interest crosses the threshold for that payer, at a higher rate if you have not given a PAN, and Form 15G or 15H stops the deduction only if your total income is genuinely below the taxable limit. The figure above is pre-tax.
Can I lend cash to a relative and charge simple interest?
Charging interest is fine; taking the money in cash may not be. Section 269SS of the Income Tax Act bars accepting a loan or deposit of ₹20,000 or more other than by cheque, bank draft or electronic transfer, and section 269T applies the same restriction to repaying it. Keep the loan on a bank trail, write down the rate and the date, and both of you can prove what the interest was.
This page starts from typical figures. In Hundo the same calculator opens on your own — the loan, the deposit, the salary already on the ledger — and says where each number came from.