Short answer: A flat interest rate charges interest on your full original loan amount for the entire tenure, even as you repay it. A reducing balance rate charges interest only on your outstanding balance, which falls with every EMI. This makes a flat rate far more expensive than it looks: a flat rate of, say, 10 percent is roughly equivalent to an 18 percent reducing balance rate. Always compare loans on a reducing balance basis.
This is one of the most important, and most misunderstood, ideas in borrowing. Get it wrong and you can overpay significantly. Here is how it works.
The core difference
The two methods calculate interest very differently:
- Flat rate: interest is charged on the full original loan amount for the whole tenure, regardless of how much you have already repaid.
- Reducing balance rate: interest is charged only on the outstanding balance, which shrinks with every EMI you pay.
With a reducing balance rate, as you pay down your loan, your interest falls too. With a flat rate, you keep paying interest on money you have already given back, which is exactly why it costs more.
A clear example
Take a loan of 1,00,000 for 2 years:
- At a 10 percent flat rate: interest is 10 percent of 1,00,000 each year, so 20,000 over two years. You repay 1,20,000, an EMI of 5,000.
- The same repayment on a reducing balance basis works out to an effective rate of roughly 18 percent.
In other words, a “10 percent flat” loan is not a 10 percent loan at all. Its true cost is nearly double, because you are charged interest on the original amount even as your balance falls.
The rule of thumb
As a quick guide, a flat rate is roughly equivalent to 1.7 to 1.9 times the reducing balance rate for typical tenures. So:
- A 10 percent flat rate is roughly an 18 percent reducing rate.
- A 12 percent flat rate is roughly a 21 to 22 percent reducing rate.
This is why a flat rate that looks cheaper than a reducing rate almost always costs you more. The label is misleading by design.
Flat vs reducing: side by side
| Feature | Flat Rate | Reducing Balance Rate |
|---|---|---|
| Interest charged on | Full original amount, whole tenure | Outstanding balance only |
| As you repay | Interest stays the same | Interest reduces |
| Headline rate | Looks lower | Looks higher |
| True cost | Higher | Lower (fairer) |
| Common on | Some consumer, vehicle, and informal loans | Most bank and NBFC personal loans |
How to protect yourself
Because a flat rate is designed to look attractive, a few habits keep you from overpaying:
- Always ask for the reducing balance rate, or the effective annual rate (APR), so you can compare like with like.
- Never compare a flat rate against a reducing rate directly. Convert them, or ask the lender to quote both.
- Be wary of unusually “low” flat rates, especially on consumer-durable, used-vehicle, or informal loans, where flat rates are common.
- Focus on the total amount repayable, not just the headline rate or the EMI. The total cost tells the real story.
Most reputable bank and NBFC personal loans are quoted on a reducing balance basis, which is the fairer method. Knowing the difference means you can never be caught out by a tempting flat rate again.
Frequently asked questions
What is the difference between flat and reducing interest rates?
A flat rate charges interest on the full original loan amount for the entire tenure. A reducing balance rate charges interest only on the outstanding balance, which falls as you repay, making it cheaper.
Is a flat rate cheaper than a reducing rate?
No. A flat rate looks lower but is actually more expensive. A flat rate is roughly equivalent to 1.7 to 1.9 times the reducing balance rate, so a 10 percent flat rate is about an 18 percent reducing rate.
Why do lenders quote flat rates?
Because a flat rate produces a lower-sounding number than the equivalent reducing rate, which can make a loan appear cheaper than it is. Always compare on a reducing basis.
Which rate do most personal loans use?
Most reputable bank and NBFC personal loans use the reducing balance method, which is fairer. Flat rates are more common on some consumer, vehicle, and informal loans.
How do I compare two loans fairly?
Compare them on the same basis, either the reducing balance rate or the effective annual rate (APR), and look at the total amount repayable rather than just the headline rate.
With Jupiter: you can check your eligibility for a personal loan and see the rate, EMI, and total repayment upfront. Related reading: what determines your loan interest rate and fixed vs floating rates.
Borrow with the real numbers
The best defence against a misleading rate is transparency. In the Jupiter app, you can check your eligibility for a personal loan and see the rate, EMI, and total repayment clearly upfront, so you always know the real cost. Jupiter is the 1-app for everything money.
Interest rate methods and terms vary by lender. Figures here are illustrative and rounded for clarity. Loans on Jupiter are facilitated in partnership with RBI-registered NBFCs. This article is general information, not financial advice. Please borrow responsibly.
