Two loans, one number
A dealer's finance desk offers ₹5 lakh at "7%". A bank quotes 11% for the same amount. The dealer looks four points cheaper. Then you read the fine print: the dealer's 7% is a flat rate, and the bank's 11% is on a reducing balance. Those are two different ways of charging interest, and the word "flat" changes the price by more than the gap between the numbers.
A reducing-balance rate charges interest each month only on what you still owe. A flat rate charges interest on the full amount you borrowed, for every year of the loan, as if you never repaid a rupee. It is simple interest on the original principal, divided into equal instalments.
The same 7%, both ways
₹5 lakh for three years at 7%, computed both ways:
| 7% flat | 7% reducing | |
|---|---|---|
| EMI | ₹16,806 | ₹15,439 |
| Total interest | ₹1,05,000 | ₹55,788 |
| Extra cost of the flat method | ₹49,212 |
The flat interest is simply ₹5 lakh × 7% × 3 years. The reducing figure comes from the standard EMI formula that the EMI calculator uses, and it is lower because the balance shrinks every month.
The year-by-year split shows where the gap comes from:
| Year | Flat interest | Reducing interest | Reducing balance at year end |
|---|---|---|---|
| 1 | ₹35,000 | ₹30,084 | ₹3,44,822 |
| 2 | ₹35,000 | ₹18,866 | ₹1,78,425 |
| 3 | ₹35,000 | ₹6,837 | ₹0 |
In year three you owe, on average, just under ₹1 lakh. The flat loan still charges 7% on ₹5 lakh. How an EMI actually works explains the reducing schedule in more detail.
What 7% flat really is
The fair comparison is the reducing rate that produces the same EMI as the flat quote. There is no closed formula for it, so the flat vs reducing calculator solves for it, and the arithmetic below follows the same method. For a 7% flat quote on ₹5 lakh:
| Tenure | Flat EMI | Flat interest | Reducing-rate equivalent | Multiple of 7% |
|---|---|---|---|---|
| 1 year | ₹44,583 | ₹35,000 | 12.68% | 1.81 |
| 2 years | ₹23,750 | ₹70,000 | 12.91% | 1.84 |
| 3 years | ₹16,806 | ₹1,05,000 | 12.83% | 1.83 |
| 4 years | ₹13,333 | ₹1,40,000 | 12.68% | 1.81 |
| 5 years | ₹11,250 | ₹1,75,000 | 12.50% | 1.79 |
| 7 years | ₹8,869 | ₹2,45,000 | 12.16% | 1.74 |
So the dealer's 7% flat is roughly a 12.8% loan. The bank's 11% reducing is cheaper: its EMI is ₹16,369 and its interest ₹89,297 over three years, ₹15,703 less than the flat offer. A bank loan at 12.5% would cost ₹1,02,165 in interest, almost exactly the flat offer's ₹1,05,000, with an EMI of ₹16,727 against ₹16,806. The rates in this example are illustrative, not current offers.
The multiple barely moves with the flat rate. Over three years:
| Flat rate | Reducing equivalent |
|---|---|
| 5% | 9.31% |
| 6% | 11.08% |
| 8% | 14.55% |
| 9% | 16.24% |
| 10% | 17.92% |
| 12% | 21.20% |
The rule of thumb
Multiply a flat rate by about 1.8 for loans of one to five years. That gets you within a few tenths of a point. The textbook shortcut, flat rate × 2n ÷ (n + 1) with n the number of EMIs, gives 13.62% for 7% flat over 36 months, about 0.8 point too high. It is a useful upper bound, not the answer.
The reason is intuitive. Over the life of an evenly repaid loan your average balance is a little over half of what you borrowed, so charging interest on the whole amount roughly doubles the true rate. The multiple slips a little on long tenures, but on a seven-year loan it is still 1.74.
Where flat rates turn up
Bank home loans, car loans and most personal loans are quoted on a reducing balance. Flat quotes survive in dealership vehicle finance, some consumer-durable and NBFC personal loans, informal lending, and some two-wheeler and used-car offers. The 20/4/10 car rule post warns about flat car-loan quotes for this reason; check any car quote on the car loan EMI calculator after converting it, and price the car itself with the car on-road price calculator.
The pitfalls
Comparing EMIs instead of rates. A flat loan's EMI can sit within a few hundred rupees of a reducing loan at a much higher headline rate, as the 12.5% example shows. Matching EMIs mean matching prices.
Ignoring fees. Processing charges with 18% GST sit on top of either method and push the real cost higher still. Our post on processing fees, GST and the true APR runs a ₹5 lakh personal loan through them.
Paying early. On a flat loan the interest is fixed on day one. Before signing, ask in writing how a foreclosure amount is worked out, because that decides whether prepaying saves anything. On a reducing loan the loan prepayment calculator shows the saving directly.
"No-cost" EMIs. A card or store EMI with no interest usually means a discount you did not get. Credit card rewards without the debt trap covers how card EMIs are priced.
Not asking for the APR. RBI's Key Facts Statement rules require lenders to give retail borrowers a standard summary with the annual percentage rate (APR) before the loan is signed. The APR counts interest on what you actually owe, plus the charges, much as an XIRR does for an investment's cash flows, so it puts a flat quote and a reducing quote on one scale.
For a short, small loan the gap may be a few thousand rupees. On ₹5 lakh over three years it is ₹49,212 at the same headline 7%. If you are choosing between borrowing routes altogether, gold loan vs personal loan vs credit card compares their real costs, and prepay, refinance or invest covers what to do once the loan is running.
For education only, not financial advice. Rates in the examples are assumed, not current offers. Read the lender's Key Facts Statement before signing.
Frequently asked questions
What is a flat 7% interest rate in reducing-balance terms?
On a ₹5 lakh loan over three years, a 7% flat rate gives the same EMI, ₹16,806, as a 12.83% reducing-balance rate. Across tenures of one to five years the equivalent stays between 12.5% and 12.9%, roughly 1.8 times the flat figure.
Why is a flat interest rate more expensive?
A flat rate charges interest on the full original loan for the whole tenure, even though you repay principal every month. On ₹5 lakh at 7% flat over three years you pay ₹35,000 of interest in the final year, when a reducing-balance loan at 7% would charge only ₹6,837.
How do I convert a flat rate to a reducing rate quickly?
Multiply by about 1.8 for loans of one to five years. The textbook shortcut, flat rate times 2n divided by n plus 1 where n is the number of EMIs, overstates it slightly: 13.62% against an exact 12.83% for 7% flat over 36 months. The flat vs reducing calculator gives the exact figure.
This is commentary on published data, not investment advice. WealthTicker is not a SEBI-registered adviser or distributor. Figures are as of the dates stated and can be revised by their source.
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