Last updated 12 Nov 2026
A flat interest rate charges interest on the original loan amount for the whole tenure, even though you repay part of it every month. A reducing-balance rate charges interest only on the amount you still owe. For the same quoted number, the flat rate costs you much more: in the example below, 12% flat on a three-year loan costs about the same as a reducing-balance rate of about 21% a year.
Two lenders can quote 12% and charge very different amounts. The difference is how the interest is worked out. This guide shows the arithmetic, explains how to spot which method a quote uses, and tells you how to compare any two offers on equal terms.
Reducing-balance (diminishing) interest
Each month, interest is worked out on the principal still outstanding. Your EMI stays the same, but its make-up changes: early on, most of it is interest; later, most of it is principal. As the balance falls, so does the interest. Home loans, most personal loans and most bank loans work this way. See reducing-balance interest and amortisation.
Flat interest
Interest is worked out on the original amount for the full tenure and added to the loan. The total is then divided into equal instalments. Because the interest does not fall as you repay, you pay interest on money you have already returned. Some vehicle, consumer and small-ticket loans are quoted this way. See flat interest rate.
A worked example
The numbers below are illustrative only and are not a rate any lender offers. They are for arithmetic. Suppose you borrow ₹4,00,000 for 3 years (36 months) and the quoted rate is 12% a year.
Flat and reducing-balance compared, same quote, same loan
| Item | Flat 12% | Reducing balance 12% |
|---|---|---|
| Loan amount | ₹4,00,000 | ₹4,00,000 |
| Tenure | 36 months | 36 months |
| How interest is worked out | ₹4,00,000 x 12% x 3 years | Each month on the balance still owed |
| Total interest | ₹1,44,000 | About ₹78,286 |
| Total you repay | ₹5,44,000 | About ₹4,78,286 |
| EMI | About ₹15,111 | About ₹13,286 |
| Extra you pay on the flat quote | About ₹65,714 more in total | Not applicable |
| Equivalent reducing-balance rate | About 21% a year | 12% a year |
The flat quote costs about ₹65,714 more over the life of the loan, and the EMI is about ₹1,825 higher every month. A flat 12% behaves like a reducing-balance rate of about 21% a year.
How the reducing-balance EMI is split
On the reducing-balance loan, the EMI of about ₹13,286 is the same every month, but the split shifts. This table shows why paying early saves interest.
Selected months of the reducing-balance loan (approximate)
| Month | Interest part | Principal part | Balance after the payment |
|---|---|---|---|
| 1 | ₹4,000 | ₹9,286 | ₹3,90,714 |
| 2 | ₹3,907 | ₹9,379 | ₹3,81,336 |
| 12 | ₹2,926 | ₹10,360 | ₹2,82,234 |
| 24 | ₹1,612 | ₹11,674 | ₹1,49,532 |
| 36 | ₹132 | ₹13,154 | ₹0 |
After 12 months you have paid about ₹1,59,430 in EMIs and still owe about ₹2,82,234. On the flat loan you would have paid about ₹1,81,332 in the same time, and the quote does not make it obvious how much of the principal you have cleared. This is why a flat quote is harder to judge.
Why lenders use flat rates
- The number looks lower than a reducing-balance quote on a similar loan, which makes it easy to market.
- It is simple to calculate and explain: total interest divided over the months.
- It is common on short, small-ticket products where a borrower thinks in terms of a fixed monthly outgo.
There is nothing unlawful in quoting a flat rate if the agreement and the Key Fact Statement state the real cost. The Key Fact Statement must show the APR, which puts interest and fees on one yearly basis so you can compare. See Key Fact Statement and APR.
How to compare any two offers
What to check
| Question | Why it matters |
|---|---|
| Is the rate flat or reducing-balance? | This decides how much interest you pay for the same number |
| What is the APR in the Key Fact Statement? | It brings interest and fees into one yearly figure on a common basis |
| What is the total amount payable? | Compare the rupee total, not only the rate |
| Is the rate fixed or floating? | A floating rate can change and your EMI or tenure can change with it |
| What are the processing fee, foreclosure and part-payment terms? | Set by the lender; they change the true cost |
| What does prepayment save me? | On reducing-balance loans it cuts later interest; on flat loans it depends on the lender's terms |
The flat vs reducing calculator and the EMI calculator do these sums for you. For current indicative rates, see the interest rates page.
Does prepaying a flat-rate loan save interest?
On a reducing-balance loan, every rupee you prepay stops earning interest from that day, so the saving is clear. On a flat-rate loan, the interest was fixed up front, so the saving depends on the lender's rule for early closure. Some lenders use a formula that returns part of the interest; others do not. Ask for the foreclosure statement in writing before you decide. Read Loan prepayment and foreclosure.
Spotting a flat rate in the wild
- The advertisement says "interest as low as" and shows a rate with no mention of "reducing balance" or "APR".
- The offer shows a total interest figure and a flat EMI, and the interest is the same in every month of the schedule.
- The statement of account shows the same interest amount each month, even after you have repaid a lot of principal.
- The salesperson gives you a rate and an EMI but cannot show you the repayment schedule.
If any of these fits, ask for the Key Fact Statement and the full repayment schedule. A reducing-balance schedule shows interest falling every month and principal rising. If the schedule does not, you are looking at a flat structure.
A quick way to estimate the equivalent rate
A rough rule is that a flat rate behaves like a reducing-balance rate nearly twice as high, because on average you owe only about half the original amount over the tenure. In the example, 12% flat behaves like about 21% reducing. The gap grows with longer tenures and is not exact, so use a calculator and the APR. Treat the rule as a warning sign, not as a figure to quote.
Frequently asked questions
Why does a flat rate cost more than a reducing rate with the same number?
A flat rate applies to the full original amount for the whole tenure, even though you keep repaying. A reducing rate applies only to what you still owe. So the flat rate charges interest on money you have already returned.
Is a reducing rate always cheaper?
For the same quoted number, yes. But two offers with different numbers can reverse that, and fees matter too. Compare the APR and the total amount you will pay, not the headline rate.
How do I convert a flat rate to a reducing rate?
There is no single multiplier. You need the tenure, because the equivalent rate changes with it. The simplest way is to take the EMI, the loan amount and the tenure and use the flat vs reducing calculator or the EMI calculator to find the rate.
Do home loans use flat rates?
Home loans from banks and housing finance companies are generally on reducing balance. Flat quotes are more common on some vehicle, consumer and small-ticket loans. Always ask.
Where can I see the APR?
In the Key Fact Statement the lender must give you before you accept the loan. It shows the APR along with the loan amount, charges and repayment schedule.
Does the advertised rate include fees?
Usually not. The headline rate covers interest only. Processing and other fees are set by the lender and shown separately. The APR is the figure that includes them.
Related reading: Fixed vs floating interest rate, Loan prepayment and foreclosure, Key Fact Statement and APR, Repo rate, EBLR and MCLR explained, Loan eligibility and FOIR, Reducing-balance interest, APR, Flat vs reducing calculator, EMI calculator, Interest rates.