EMI Explained: How Banks Calculate Your Loan EMI

EMI, or Equated Monthly Installment, is the fixed amount you pay every month to repay a loan. Whether it's a home loan, personal loan, or vehicle loan, the underlying math banks use is the same formula — even though the numbers on your loan statement can look confusing at first glance.

The EMI formula

Banks calculate EMI using three inputs: the principal loan amount, the monthly interest rate, and the total number of monthly installments (the tenure in months).

• P = Principal loan amount
• R = Monthly interest rate (annual rate divided by 12, then divided by 100)
• N = Loan tenure in months
• EMI = [P × R × (1+R)^N] / [(1+R)^N − 1]

This looks intimidating, but the logic behind it is simple: the formula spreads both the principal and the compounding interest evenly across every month of the tenure, so you pay the same amount each month even though the underlying principal-to-interest ratio shifts over time.

Why your early EMIs are mostly interest

This is the part that surprises most first-time borrowers. In the early months of a loan, a much larger share of your EMI goes toward interest rather than principal, because interest is calculated on the outstanding balance, which is highest at the start. As you keep paying, the outstanding principal shrinks, so a growing share of each EMI goes toward paying down the actual loan rather than interest. This is called an amortization schedule.

Worked example

Take a loan of ₹10,00,000 at 9% annual interest over 20 years (240 months). The monthly interest rate works out to 0.75%. Plugging these into the formula gives an EMI of roughly ₹8,997 per month. Over the full 20-year tenure, total repayment comes to around ₹21,59,280 — meaning total interest paid is about ₹11,59,280, more than the original loan amount itself.

This is why loan tenure matters as much as the interest rate. A shorter tenure raises the monthly EMI but sharply cuts total interest paid, since less time means less compounding.

What changes between loan types

The EMI formula itself doesn't change between a home loan, personal loan, or car loan. What differs is the interest rate offered (personal loans are typically priced higher than secured loans like home or car loans, since they carry no collateral) and the maximum tenure a lender will allow.