Flat vs reducing interest rate
A low flat rate can cost more than a higher reducing-balance rate. Check which method the quote uses, convert it to a reducing rate, and only then compare the EMIs.
What you'll learn:
- How each method works
- Where flat rates still appear
- Convert a flat rate to reducing
Key takeaways
- Flat rate charges interest on the original principal for the full tenure; reducing balance charges interest only on what you still owe.
- Indian bank home, car, and personal loans usually use reducing balance. Flat quotes still appear in some dealer and two-wheeler finance.
- A lower flat percentage can still cost more than a higher reducing-balance percentage. Compare EMI, total interest, and APR, not the advertised % alone.
- This site's EMI calculator and EMI formula page both use reducing balance.
Total interest: 7% flat vs reducing-balance quotes
| Point | Total interest |
|---|---|
| 7% · flat | ₹1,75,000 |
| 10% · reducing | ₹1,37,411 |
| 11% · reducing | ₹1,52,273 |
| 12% · reducing | ₹1,67,334 |
| 13% · reducing | ₹1,82,592 |
Flat to reducing rate converter
Enter the flat rate from a dealer or lender quote. See the EMI it implies and the reducing-balance rate that gives the same EMI.
- Equivalent reducing rate
- -
- EMI on the flat quote
- -
- Total interest, flat
- -
- EMI if the same % were reducing
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- Extra you pay on flat
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Definition
Flat rate and reducing balance are two ways to charge interest on an EMI loan. The percentage on the brochure is not enough by itself. You need to know which method sits behind that percentage.
On a flat rate, interest is calculated on the full original principal for the entire tenure, even after you have repaid some of it. On a reducing balance (also called diminishing balance), each month’s interest is calculated only on the outstanding principal. As the balance falls, the interest portion of the EMI usually falls too.
Indian banks and most NBFCs price home loans, personal loans and car loans on reducing balance. Flat quotes still show up in dealer finance, some two-wheeler schemes and a few consumer durable offers. This site’s EMI calculator and the EMI formula page both use reducing balance.
How each method works
Reducing balance
Take a ₹5 lakh loan at 10% a year for 36 months. Monthly rate is 10 ÷ 12 ÷ 100 = 0.008333. Month 1 interest is about ₹4,167 on the full ₹5 lakh. After that EMI clears some principal, month 2 interest is charged on the smaller balance.
Approximate schedule at the start:
| Month | Interest | Principal repaid | Closing balance |
|---|---|---|---|
| 1 | ₹4,167 | ₹11,967 | ₹4,88,033 |
| 2 | ₹4,067 | ₹12,067 | ₹4,75,966 |
| 3 | ₹3,966 | ₹12,167 | ₹4,63,799 |
EMI stays near ₹16,134. By the final month, interest is only a few hundred rupees. Total interest over three years is about ₹80,809.
Flat rate
Same ₹5 lakh, 10%, 36 months, but flat:
total interest = principal × annual rate × years
That is ₹5,00,000 × 10% × 3 = ₹1,50,000. Add principal and divide by 36. EMI comes to about ₹18,056. Interest does not shrink with the balance; the quote locked it in on day one.
Same rate, different bill
Hold principal and tenure fixed and change only the method:
| Quote | Method | Approx. EMI | Approx. total interest | Approx. total paid |
|---|---|---|---|---|
| 10% for 3 years on ₹5 lakh | Reducing | ₹16,134 | ₹80,809 | ₹5,80,809 |
| 10% for 3 years on ₹5 lakh | Flat | ₹18,056 | ₹1,50,000 | ₹6,50,000 |
The flat quote uses the same “10%” label and costs about ₹69,000 more in interest.
A second check: ₹10 lakh at 12% for 5 years.
| Method | Approx. EMI | Approx. total interest |
|---|---|---|
| Reducing | ₹22,244 | ₹3,34,667 |
| Flat | ₹26,667 | ₹6,00,000 |
If you force the flat EMI of about ₹18,056 onto a reducing-balance schedule for the ₹5 lakh case, the equivalent reducing rate is close to 18%. Rough thumb rules (multiply flat by 1.7 to 1.9) exist online. They drift with tenure, so prefer an exact schedule or APR.
Run your own numbers in the EMI calculator or the compare loan offers tool. For a car or personal loan quote, use the matching car loan or personal loan page.
Where flat rates still appear
You are more likely to see a flat quote when:
- A dealer or showroom is arranging the loan.
- The product is a two-wheeler or consumer durable scheme.
- Marketing copy leads with a single low percentage and no repayment schedule.
Bank home loan EMI offers are almost always reducing balance. If a home loan brochure ever shows a flat figure, treat it as a red flag and ask for the reducing-balance rate in writing.
Flat is not the same as fixed. Fixed vs floating is about whether the rate can move with a benchmark. Flat vs reducing is about which principal the interest sits on. A loan can be fixed-rate and reducing-balance at the same time. For rate resets after disbursal, see the floating rate guide.
How to compare two quotes
- Ask: is this percentage flat or reducing balance?
- Ask for total interest payable and total amount payable over the full tenure.
- Ask for APR from the Key Facts Statement, where the lender is RBI-regulated.
- Enter both offers with the same principal and months in compare loan offers.
- Add processing fees and other compulsory charges outside the EMI if they are not already in APR.
From October 2024, RBI-regulated entities must give retail and MSME borrowers a Key Facts Statement before sanction. That sheet includes APR and an amortisation schedule. APR on the KFS is worked out on a reducing-balance basis, which is why two loans with the same advertised rate can show different APRs when one quote was flat.
If a seller will not share total payable or a schedule, do not treat the percentage as comparable. Rebuild the EMI yourself from principal, reducing-balance rate and months, then decide.
Sources and further reading
- RBI: Key Facts Statement (KFS) for Loans & Advances (15 April 2024): APR and amortisation schedule before sanction; APR examples use the reducing-balance method.
- Lender Key Facts Statement and sanction letter: the binding rate type and schedule for your loan.
- EMI formula: reducing-balance math used on this site.
For how fees weigh on short loans, also read compare loan offers and the interest rate guide.