Flat vs Reducing-Balance Interest: Why Your Loan Costs More Than You Think
Updated 22 June 2026
Two loans can advertise "10% interest" and cost wildly different amounts. The trick is whether it's a flat or reducing-balance rate — and it's where borrowers overpay the most.
Flat rate
Interest is charged on the original principal for the whole tenure — even though you're steadily paying the loan down. So you keep paying interest on money you've already repaid.
Reducing-balance rate
Interest is charged only on the outstanding balance, which drops every month. This is the honest way to price a loan, and it's what credit cards, home loans, and most banks use.
The gap is bigger than it looks
For the same headline number, a flat rate's true (effective) cost is often close to double. A "10% flat" loan can work out to roughly 18–19% on a reducing-balance basis over a typical tenure. That's a huge difference on a large loan.
How to protect yourself
- Always ask for the effective annual rate (APR), not the flat rate.
- Compare loans only on the reducing-balance / effective rate.
- If only a flat rate is quoted, that itself is a mild red flag — ask why.
Check your loan agreement
The loan agreement checker flags when a flat rate is hiding the true cost, along with other loan red flags. See also loan agreement red flags.
General information for borrowers in India, not financial advice.
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Open the checker →FAQ
- What's the difference between a flat and reducing-balance interest rate?
- A flat rate is charged on the original principal for the entire tenure, even as you repay. A reducing-balance rate is charged only on the outstanding balance, which falls each month. For the same headline number, a flat rate costs you much more.
- How much higher is a flat rate really?
- Roughly, a flat rate's effective (reducing-balance) cost is often close to double the flat number — e.g. a 10% flat rate can work out to ~18–19% effective over a typical tenure. Always ask for the effective annual rate (APR).
- How do I compare loans fairly?
- Compare on the effective/reducing-balance rate (APR), not the flat rate. If a lender only quotes a flat rate, ask them to convert it, or compute the EMI and derive the effective rate.