Flat vs Reducing Rate Calculator
See how much more a loan costs when interest is charged on a flat rate versus a reducing balance.
- Reducing
- Flat
- Principal
- ₹5.00L
- Interest at a reducing rate
- ₹97.86K
- Extra paid on a flat rate
- ₹82.14K
A flat rate charges interest on the full loan amount for the whole tenure, while a reducing-balance rate charges only on the outstanding balance — so the same nominal 12% costs much more as a flat rate.
Independent · No commissions · No fund-house data — how the numbers are computed
How it works
This calculator compares the two ways lenders quote loan interest. A reducing-balance rate charges interest only on the principal still outstanding, falling every month as EMIs are paid. A flat rate charges interest on the full original loan amount for the entire tenure, as if nothing were ever repaid. Enter one loan and one nominal rate, and it computes both EMIs, both interest totals, and the extra a flat rate costs.
The gap is large and systematic. At the calculator's defaults — ₹5 lakh at 12% over 3 years — the reducing-balance loan costs about ₹97,900 in interest while the flat-rate version costs ₹1,80,000: roughly ₹82,000 extra for the same headline number. As a rule of thumb, a flat rate's true reducing-balance equivalent is around 1.8 times the quoted figure, so "12% flat" behaves like a 21%+ reducing rate.
Flat rates survive because they sound cheaper. Bank home and car loans quote reducing rates; flat rates appear in vehicle financing at dealerships, personal loans from some NBFCs, and informal lending. The comparison this calculator draws — same principal, same nominal rate, both methods — is the one to run before signing anything quoted "flat".
Flat: Interest = P × R/100 × t, EMI = (P + Interest) / n. Reducing: EMI = P · r · (1+r)^n / ((1+r)^n − 1)P is the principal, R the annual rate in percent, t the tenure in years, n the tenure in months, and r the monthly rate (R ÷ 12 ÷ 100). The flat method charges R on the full P for all t years; the reducing method charges r monthly on the outstanding balance only.
Frequently asked questions
What is the difference between a flat rate and a reducing-balance rate?
A flat interest rate is applied to the original loan amount for the whole tenure — total interest is simply principal × rate × years, regardless of repayments. A reducing-balance rate charges interest each month only on the principal still outstanding, so the interest charge falls as the loan is repaid. Both produce a fixed EMI, but at the same quoted percentage the flat method collects far more interest.
How much more expensive is a flat rate than a reducing rate?
At the same quoted percentage, roughly 1.7 to 1.9 times the interest, with the exact multiple depending on tenure. On a ₹5 lakh loan at 12% over 3 years — this calculator's defaults — the reducing-balance interest is about ₹97,900 while the flat-rate interest is ₹1,80,000, an extra ₹82,000. Equivalently, a 12% flat rate costs about what a 21%+ reducing rate would.
How do I convert a flat rate to a reducing-balance equivalent?
A quick approximation is to multiply the flat rate by about 1.8 — so a 7% flat rate corresponds to roughly a 12.5% reducing rate, and 12% flat to about 21.5% reducing. The exact equivalent is the rate at which the reducing-balance EMI formula reproduces the flat loan's EMI, and it grows with tenure. The reliable comparison is total interest computed both ways on the same loan, which is exactly what this calculator does.
Which loans in India are quoted at flat rates?
Bank home loans, car loans and most personal loans are quoted on a reducing-balance basis, as RBI transparency norms push lenders toward effective-rate disclosure. Flat rates persist mainly in dealership vehicle finance, some NBFC personal and consumer-durable loans, gold loans from informal lenders, and private lending. Any quote using the word "flat" — however low the number — should be converted to a reducing-balance equivalent before comparing.