What is a flat vs reducing rate calculator?
Some lenders quote interest on a flat-rate basis while most bank loans use reducing balance (diminishing) interest. The same headline rate can produce very different EMIs and total interest costs.
This calculator compares both methods side by side for the same loan amount, tenure, and annual interest rate—so you can see monthly EMI, total interest, and total repayment under each method.
Flat rate vs reducing balance — what's the difference?
Under flat rate, interest is calculated on the original principal for the entire tenure. Under reducing balance, interest is charged only on the outstanding principal after each EMI, which falls every month.
- Flat rate keeps the same principal base for interest all tenure, so total interest is often much higher than reducing balance even when the quoted rate looks similar.
- Reducing balance is the standard method for home loans, car loans, and personal loans from banks.
- Always ask whether a quoted rate is flat or reducing before comparing offers.
How does this calculator work?
Flat rate: Total Interest = (P × I × T) / 100; EMI = (Principal + Total Interest) / (T × 12). Reducing balance uses the standard amortizing EMI formula—the same as our EMI calculator.
Flat interest = (P × I × T) / 100
Where –
| P | Loan amount (principal) |
|---|---|
| I | Annual interest rate (%) |
| T | Loan tenure in years |
Reducing balance EMI = P × r × (1 + r)^n / ((1 + r)^n − 1)
Worked example
Borrow ₹10,00,000 at 10% per year for 5 years. Flat rate EMI is ₹25,000 with ₹5,00,000 total interest. Reducing balance EMI is about ₹21,247 with roughly ₹2,74,823 total interest—you save about ₹2,25,177 with reducing balance on the same quoted rate.
How to use this calculator
Enter loan amount, rate of interest (p.a.), and loan tenure in years. The comparison table and charts update instantly as you move the sliders.
What this calculator does not include
Processing fees, insurance, prepayment charges, and GST on fees are not modeled. Some lenders may use slightly different rounding on EMI schedules.
Frequently asked questions
Which method is cheaper — flat or reducing?
For the same nominal rate, reducing balance almost always costs less in total interest because you pay interest on a shrinking principal. Flat rate keeps interest on the full principal for the entire tenure.
Do banks use flat or reducing balance?
Most regulated bank loans in India use reducing balance. Flat-rate quotes are more common in certain NBFC, gold-loan, or short-term product brochures—always confirm before signing.
Can I compare this with home or car loan EMIs?
Yes. Use the home loan or car loan EMI calculators for product-specific defaults; this tool is for understanding the interest method difference on the same inputs.