How EMI Is Calculated: Formula, Example and Breakup

EMI (equated monthly instalment) is calculated with the reducing-balance 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 months. For a ₹30 lakh home loan at 8.5% for 20 years, that works out to about ₹26,035 a month. Below is how the formula works, a step-by-step example, and what happens inside each EMI.

What an EMI actually is

An EMI is a fixed monthly payment that repays a loan in full over a set tenure. Every instalment has two parts:

• Interest for that month, charged on the principal still outstanding.
• Principal repayment, which is whatever is left of the EMI after interest.

Because the EMI stays constant while the outstanding balance keeps falling, the interest part shrinks every month and the principal part grows. This is called a reducing-balance (or amortising) loan, and it is how almost all home, car and personal loans from Indian banks and NBFCs are structured.

The EMI formula explained

EMI = P × r × (1 + r)^n / ((1 + r)^n − 1)

Two points trip people up:

1. r must be monthly and in decimal form. 8.5% a year becomes 8.5 ÷ 12 ÷ 100 = 0.0070833.
2. n is in months, not years. A 20-year loan has 240 instalments.

The formula comes from setting the present value of all future EMIs equal to the loan amount. In plain terms, it finds the single monthly payment that, after interest is added each month, brings the balance to exactly zero on the last instalment.

Worked example: ₹30 lakh home loan at 8.5% for 20 years

Step 1: Convert the inputs.

• P = ₹30,00,000
• r = 8.5 ÷ 12 ÷ 100 = 0.0070833
• n = 20 × 12 = 240

Step 2: Calculate (1 + r)^n.

(1.0070833)^240 ≈ 5.4412

Step 3: Plug into the formula.

• Numerator: 30,00,000 × 0.0070833 × 5.4412 = 21,250 × 5.4412 ≈ 1,15,626
• Denominator: 5.4412 − 1 = 4.4412
• EMI = 1,15,626 ÷ 4.4412 ≈ ₹26,035

Step 4: Total cost.

• Total paid: ₹26,035 × 240 ≈ ₹62.48 lakh
• Total interest: about ₹32.48 lakh, more than the loan itself

You can check these numbers, or try your own, with our EMI calculator.

Inside the first EMI: interest vs principal

In month 1 the full ₹30 lakh is outstanding, so:

• Interest = 30,00,000 × 0.0070833 = ₹21,250
• Principal = 26,035 − 21,250 = ₹4,785

Only about 18% of the first EMI reduces your loan. Over the whole first year, you pay roughly ₹2.53 lakh of interest and only about ₹0.60 lakh of principal. The split reverses slowly; on this loan, principal overtakes interest in the EMI only around the 12th year.

This is why prepaying early in a loan has the biggest effect. Every rupee of principal you clear early stops attracting interest for all the remaining years. Our guide on whether to reduce EMI or tenure after a home loan prepayment shows how much this can save.

How tenure changes EMI and total interest

Same ₹30 lakh loan at 8.5%, different tenures:

Going from 20 to 30 years cuts the EMI by under ₹3,000 a month but adds over ₹20 lakh in interest. A longer tenure can help you qualify for a bigger loan, but it is an expensive way to lower the monthly outgo.

How the interest rate changes EMI

Same ₹30 lakh loan for 20 years, at different rates:

Each 0.5 percentage point adds roughly ₹950 to the EMI and over ₹2 lakh to total interest on this loan. That is why a strong credit score, which helps you get a lower rate, matters so much. See how to improve your CIBIL score for practical steps.

Floating rates, the repo rate and your EMI

Most new home loans in India are floating-rate loans linked to an external benchmark, usually the RBI repo rate. The RBI's Monetary Policy Committee raised the repo rate by 25 basis points to 5.50% on 7 October 2026, the first hike since February 2023. Lenders pass benchmark changes on to floating-rate borrowers at their scheduled reset dates.

When your rate goes up, the lender has two ways to keep the loan on track:

• Increase the EMI and keep the end date the same, or
• Extend the tenure and keep the EMI the same.

Banks often default to extending the tenure, because it keeps the EMI unchanged and borrowers notice less. RBI's August 2023 circular on resetting floating rates requires lenders to tell borrowers about such changes and to offer the choice of a higher EMI, a longer tenure or a mix, along with an option to switch to a fixed rate under the lender's board-approved policy. The circular is framed around EMI-based personal loans, so check with your lender how it applies to your loan. If you can afford it, asking for a higher EMI instead of a longer tenure usually saves a lot of interest.

Flat rate vs reducing balance rate

Some lenders, especially for consumer durables and some two-wheeler or personal loans, quote a flat rate. Under a flat rate, interest is calculated on the full original loan for the whole tenure, even though you are repaying it every month.

Example: ₹1 lakh for 2 years at a 10% flat rate means interest of ₹10,000 a year, or ₹20,000 total, so the EMI is ₹1,20,000 ÷ 24 = ₹5,000. The same ₹5,000 EMI on a reducing-balance basis corresponds to an annual rate of roughly 18%. Always ask for the reducing-balance rate, or better, the Annual Percentage Rate (APR) shown in the Key Facts Statement that RBI requires lenders to give for retail loans.

Calculating EMI in Excel or Google Sheets

You do not need to work the formula by hand. Spreadsheets have a built-in function:

=PMT(8.5%/12, 240, -3000000)

This returns about 26,035. The arguments are the monthly rate, the number of months and the loan amount (entered as negative so the result is positive). To see the month-by-month split, use IPMT for the interest part and PPMT for the principal part.

Things the EMI formula does not include

The formula gives the cost of borrowing from interest alone. Your real cost can be higher because of:

• Processing fees and documentation charges (plus 18% GST on fees)
• Insurance bundled with the loan
• Pre-EMI interest on under-construction homes, where you pay only interest on disbursed amounts until full disbursement
• Late payment charges if you miss an EMI

For personal loans especially, these add-ons can push the effective rate well above the headline rate. Our personal loan interest rates guide covers how to compare offers on total cost.

Key takeaways

• EMI = P·r·(1+r)^n / ((1+r)^n − 1), with r as the monthly rate in decimal and n in months.
• A ₹30 lakh loan at 8.5% for 20 years has an EMI of about ₹26,035 and total interest of about ₹32.48 lakh.
• Early EMIs are mostly interest; principal repayment speeds up only in later years.
• Longer tenures lower EMI slightly but raise total interest sharply.
• Small rate differences add up to lakhs over a long loan, so compare APR and reducing-balance rates, never flat rates.
• When floating rates rise, consider raising your EMI instead of letting the tenure stretch.