Finance · 3 min read
Reducing Balance vs Flat Rate: Why 10% Is Not Always 10%
Two loans quoted at the same rate can differ by a factor of two in what they actually cost. The difference is one word in the fine print.
Two lenders quote you 10%. One is charging roughly twice as much as the other. Nothing in either advertisement is false.
The difference is what the rate is charged on.
The two methods
Reducing balance charges interest each month on what you still owe. You start owing the full principal, so the first month's interest is the largest it will ever be. As you repay, the balance falls and so does the interest. This is how home loans, and any properly amortising loan, work.
Flat rate charges interest on the original principal for every month of the term, regardless of how much you have repaid. In the final month, when you might owe only a few thousand rupees, you are still being charged interest as though you owed the entire original amount.
₹5,00,000 over 3 years at 10%
Flat rate. Interest is 10% of ₹5,00,000 = ₹50,000 a year, for 3 years = ₹1,50,000. Total repayable ₹6,50,000, so the monthly instalment is ₹6,50,000 ÷ 36 = ₹18,056.
Reducing balance. Using the standard EMI formula at 10% per annum over 36 months, the instalment is ₹16,134, and the total interest comes to about ₹80,800.
The flat-rate loan costs ₹69,200 more on the same principal, at the same advertised rate, over the same term. Expressed as a reducing-balance rate, that flat 10% is equivalent to roughly 17.9%.
| Flat 10% | Reducing 10% | |
|---|---|---|
| Monthly instalment | ₹18,056 | ₹16,134 |
| Total interest | ₹1,50,000 | ₹80,800 |
| Effective annual rate | ~17.9% | 10% |
Why it lands near double
Over the life of an amortising loan your average outstanding balance is roughly half the original principal. A flat rate charges you as though it were the full principal throughout. Charging the same percentage on double the average balance costs about double the interest.
The approximation "effective ≈ 1.8 to 2 × flat" holds reasonably well for typical consumer tenures. Shorter loans skew a little lower, longer ones a little higher.
"No cost EMI" is the same trick, inverted
Retail "no cost EMI" offers often work by quoting the item at full price and calling the finance free, when the same item bought outright carries a discount of roughly the interest amount. The interest has not disappeared; it has moved into the price. Ask what the cash price is. If it is lower, the difference is your interest, and you can compute the real rate from it.
Comparing offers properly
- Ask which method the rate uses. "Is that flat or reducing?" is a normal question and the answer must be in the sanction letter.
- Ignore the rate; compare the total repayable. Principal plus all interest plus all fees, for each offer, over the same tenure. That number is not ambiguous.
- Include processing fees and insurance. A 1% processing fee on a two-year loan is worth about half a percentage point of rate. Bundled insurance sold with the loan can be worth several.
- Check the prepayment terms. Flat-rate loans frequently do not reduce your interest at all if you repay early, because the interest was fixed at the outset. That makes them substantially worse for anyone who might clear the loan ahead of schedule.
Our Loan Comparison Calculator compares offers on total cost rather than headline rate, and the EMI Calculator shows what a reducing-balance instalment should look like for any principal, rate and tenure, which is the quickest way to sanity-check a quote that seems too good.
Common questions
How do I convert a flat rate to a comparable one?
A rough rule for a loan repaid in equal monthly instalments: the effective reducing-balance rate is a little under twice the flat rate. A 10% flat rate over three years works out around 18% effective. The approximation improves with longer tenures. For an exact figure, compute the EMI implied by the flat quote and then solve for the rate that produces the same EMI on a reducing balance, which is what an APR calculation does.
Where will I actually encounter flat rates?
Vehicle loans from dealers, consumer durable and "no cost EMI" retail finance, some gold loans, and a good deal of informal lending. Home loans in India are essentially always reducing balance. If a quote seems unusually low for the product type, flat rate is the first thing to check.
Is a flat rate illegal or a scam?
Neither, as long as it is disclosed. It is a legitimate way to quote a price. The problem is purely that a flat rate and a reducing-balance rate are not comparable numbers, and putting them side by side without converting makes the more expensive loan look cheaper.