EMI Calculator Formula Explained: How Your Loan EMI Is Calculated
Published 10 October 2026 · 6 min read · Clean EMI Editorial
An EMI calculator is only a button on top of one formula. Understanding it helps you see why a small change in rate or tenure moves your EMI and your total interest so much, and it lets you check any lender’s quote in a minute.
Part of the Home Loan guide series.
The formula
EMI = P × r × (1 + r)n ÷ ((1 + r)n − 1)
- P = loan amount (principal)
- r = monthly interest rate = annual rate ÷ 12 ÷ 100
- n = number of monthly instalments = years × 12
Home loans from PSU banks use the reducing-balance method: interest each month is charged only on the outstanding principal, so the early EMIs are mostly interest and the later ones mostly principal.
Worked example: ₹50 lakh at 8.5%
For a ₹50 lakh loan at an illustrative 8.5% a year, r = 0.085 ÷ 12 = 0.007083. Over 20 years (n = 240) the EMI comes to about ₹43,391. A quick check: ₹1 lakh at this rate and tenure is about ₹868 a month, so ₹50 lakh is about ₹43,400.
How tenure changes the cost (₹50 lakh at 8.5%)
| Tenure | EMI (approx.) | Total interest (approx.) |
|---|---|---|
| 10 years | ₹61,993 | ₹24.4 lakh |
| 15 years | ₹49,237 | ₹38.6 lakh |
| 20 years | ₹43,391 | ₹54.1 lakh |
| 25 years | ₹40,261 | ₹70.8 lakh |
| 30 years | ₹38,446 | ₹88.4 lakh |
Going from 20 to 30 years lowers the EMI by under ₹5,000 but adds roughly ₹34 lakh of interest. Going from 20 to 15 years raises the EMI by about ₹5,850 and saves about ₹15.5 lakh.
How the rate changes it (₹50 lakh, 20 years)
At 8% the EMI is about ₹41,822; at 8.5% about ₹43,391; at 9% about ₹44,986; at 9.5% about ₹46,607. Every 0.5% costs roughly ₹1,600 a month, or about ₹3.8 lakh over the loan.
Try it yourself
The calculator on the home loan page applies this formula. For a vehicle loan use the one on the vehicle loan page, and see Canara Bank for how a PSU lender structures repayment.
Frequently Asked Questions
What is the EMI formula?
EMI = P × r × (1+r)^n ÷ ((1+r)^n − 1), where P is the loan amount, r is the monthly interest rate and n is the number of monthly instalments.
Why is my first EMI mostly interest?
Interest is charged on the full outstanding principal at the start, so most of the early EMI goes to interest. The principal share grows every month.
Is a flat-rate EMI the same as a reducing-balance EMI?
No. Flat-rate quotes look lower but charge interest on the original amount throughout, so the true cost is higher. PSU bank home loans use reducing balance.
Does the EMI change if the rate changes?
On floating-rate loans the bank adjusts either your EMI or your remaining tenure when the benchmark rate changes. Ask which one your lender uses.
Useful free tools
- Free Credit Analyzer — Upload your CIBIL report and see which loans you may be eligible for, with an indicative EMI.
- Check my Loan Eligibility — Answer a few questions and see how your application would be routed to a PSU bank.
- Home Loan Balance Transfer Calculator — Compare your current EMI with a lower-rate loan over the same remaining tenure.
- Credit Score Enhancer — Practical steps to improve your CIBIL score before you apply for a loan.
Ready to check your eligibility?
No fee to apply. CIBIL score of 700 or above required.