How Your Loan EMI Is Calculated, With a Worked Example
The EMI formula, a Rs. 30 lakh worked example, a month-by-month split of interest and principal, and how tenure and rate change what you pay in total.
The formula behind the number
When a bank tells you your EMI is Rs. 26,035, that figure comes from one formula. ToolHive's EMI calculator uses the standard reducing-balance version:
EMI = P × r × (1 + r)n / ((1 + r)n − 1)
Here P is the loan amount, r is the monthly rate (annual rate divided by 12, then by 100) and n is the number of monthly instalments (years multiplied by 12). The calculator then multiplies the EMI by n to get the total payment and subtracts P to get total interest. Nothing else is added: no fees, no insurance, no rate changes.
This is general information to help you understand a loan, not financial advice. Your lender's sanction letter and repayment schedule are the authoritative figures.
A worked example: Rs. 30 lakh at 8.5% for 20 years
Take a loan of Rs. 30,00,000 at 8.5% a year for 20 years. The rate of 8.5% is an illustrative figure, not a current market quote. Then r = 8.5 / 12 / 100 = 0.7083% a month and n = 240. Plugging these in gives:
| Item | Amount |
|---|---|
| Monthly EMI | Rs. 26,035 |
| Total payment over 240 months | Rs. 62,48,327 |
| Total interest | Rs. 32,48,327 |
The interest is more than the amount borrowed. That surprises many first-time borrowers, but it follows directly from charging interest every month on a balance that takes two decades to fall to zero. Because the calculator works with the unrounded EMI, multiplying the displayed Rs. 26,035 by 240 gives a total a few tens of rupees higher than the tool's total. Banks round in their own way too, so a lender's statement can differ from any calculator by a few rupees.
Why early EMIs are mostly interest
Each month the lender charges interest on the balance still owed. Whatever is left of your EMI after that interest reduces the principal. At the start the balance is at its highest, so the interest slice is large. Here is the same loan month by month, worked out with a short script that mirrors the formula:
| Month | Interest part | Principal part | Balance after |
|---|---|---|---|
| 1 | Rs. 21,250 | Rs. 4,785 | Rs. 29,95,215 |
| 12 | Rs. 20,864 | Rs. 5,171 | Rs. 29,40,293 |
| 60 | Rs. 18,778 | Rs. 7,256 | Rs. 26,43,815 |
| 120 | Rs. 14,952 | Rs. 11,083 | Rs. 20,99,815 |
| 180 | Rs. 9,108 | Rs. 16,926 | Rs. 12,68,962 |
| 240 | Rs. 183 | Rs. 25,852 | Rs. 0 |
Look at month 1: out of Rs. 26,035, about 82% goes to interest. Across the whole first year you pay Rs. 3,12,420 in EMIs, and only about Rs. 59,700 of it reduces the loan. After ten years, with half the tenure gone, you still owe about 70% of the original amount.
This matters for two decisions. First, if you plan to prepay or refinance, doing it early saves much more than doing it late. Second, if you sell the property or close the loan after a few years, your outstanding balance will be much higher than you might guess from the years elapsed.
What changes the EMI most
Three inputs drive everything. Holding the Rs. 30 lakh loan at 8.5%, changing only the tenure gives:
| Tenure | EMI | Total interest |
|---|---|---|
| 15 years | Rs. 29,542 | Rs. 23,17,594 |
| 20 years | Rs. 26,035 | Rs. 32,48,327 |
| 25 years | Rs. 24,157 | Rs. 42,47,044 |
| 30 years | Rs. 23,067 | Rs. 53,04,266 |
Going from 20 to 30 years cuts the EMI by about Rs. 2,970 a month but adds roughly Rs. 20.5 lakh of interest. The monthly relief is small compared with the long-term cost. Now hold the tenure at 20 years and change only the rate:
| Rate | EMI | Total interest |
|---|---|---|
| 8.0% | Rs. 25,093 | Rs. 30,22,368 |
| 8.5% | Rs. 26,035 | Rs. 32,48,327 |
| 9.0% | Rs. 26,992 | Rs. 34,78,027 |
Each half-point on this loan is worth about Rs. 2.3 lakh over the full tenure and roughly Rs. 950 a month. The third lever is the loan amount itself: a larger down payment reduces P and scales every figure down in proportion.
A simple way to use this before you borrow
- Decide the largest EMI you can pay comfortably from take-home pay, not gross pay. Many lenders look at the share of income going to all EMIs, which you can test with the loan eligibility calculator.
- Enter the amount, the rate quoted in writing and a realistic tenure into the EMI calculator.
- Try a shorter tenure. If you can afford a slightly higher EMI, the interest saving is large.
- Plan how you would use windfalls such as a bonus. The loan prepayment calculator shows the effect of a lump sum at a point you choose.
Treat the EMI as one input to a household budget. It should sit alongside an emergency fund and your other goals, such as regular saving with a SIP, rather than use up every spare rupee.
Checking your lender's schedule against the calculator
Once a lender sends a repayment schedule, you can test it with the formula above. Enter the same amount, rate and tenure into the calculator and compare the EMI. If your lender's figure is higher by more than a few rupees, ask why. Common reasons are a different rate than the one advertised, a fee or insurance premium rolled into the loan amount, or a tenure counted differently. Also check how the first instalment is treated: some lenders charge pre-EMI interest on the amount disbursed so far, which makes the first payment different from the regular EMI. A short written question to the lender before signing is far easier than disputing the schedule later.
Limits: what the EMI calculator does not cover
- Floating rates. Many home loans are linked to an external benchmark. When the rate moves, your lender changes the EMI or the tenure. The tool assumes one fixed rate for the entire period.
- Fees and charges. Processing fees, GST on fees, insurance premiums and any other charges are not included.
- Moratorium or step-up plans. Education loans with a moratorium and builder-linked disbursements, where interest is charged only on the amount released so far, follow different schedules. The tool computes a plain fully disbursed loan.
- Part payments. It does not show a month-by-month schedule or what happens when you prepay. The table above was produced separately with the same formula; the calculator itself shows only the EMI, total interest and total payment.
- Tax benefits. Deductions on home loan interest depend on your tax regime and the rules in force, and they are not modelled here.
Use the calculator to compare offers on equal terms and to understand how a loan behaves. Then check the lender's key facts statement and repayment schedule before signing.