The EMI Formula, Demystified (With a Real Example)
You sign the loan papers, and a few days later your bank tells you the monthly figure: ₹12,668, or whatever it happens to be. But where does that number actually come from? It isn't a guess, and it isn't simple division. There's one formula doing all the work, and once you've seen it, loan offers stop feeling like a black box.
The formula itself
Every reducing-balance EMI is worked out like this:
EMI = P × r × (1 + r)n ÷ [ (1 + r)n − 1 ]
- P is the amount you borrow.
- r is the monthly rate — take the annual rate, divide by 12, then by 100.
- n is how many monthly payments you'll make in total.
That's the whole thing. The intimidating part is just the exponent, which is the formula's way of accounting for interest compounding month after month.
Let's plug in real numbers
Say you borrow ₹10,00,000 at 9% a year for 10 years. First convert the inputs: r becomes 0.09 ÷ 12 = 0.0075, and n becomes 10 × 12 = 120 payments. Drop those into the formula and you land on roughly ₹12,668 per month. Over ten years that adds up to about ₹15.2 lakh — meaning you pay around ₹5.2 lakh in interest on top of the original loan.
That last sentence is the one worth sitting with. The EMI looks manageable; the total interest is the real cost.
Why the early payments feel like they go nowhere
Here's something that surprises a lot of first-time borrowers. In the opening months, the bulk of your EMI is interest, and only a sliver chips away at the principal. That balance flips slowly over the years. By the final stretch, almost the entire payment is reducing your loan. This is exactly why prepaying early saves so much more than prepaying late — you're knocking out principal before years of interest pile onto it.
The three levers you control
Only three things move your EMI: the amount, the rate, and the tenure. The rate is mostly set by the market. The amount is set by what you're buying. That leaves tenure as your real dial. Stretch it out and the monthly number drops, but you'll hand the bank far more interest. Shorten it and you pay less overall, but the monthly squeeze is tighter. There's no universally "right" answer — only the one that fits your cash flow.
If you'd rather not do the arithmetic by hand, our EMI Calculator runs the formula instantly and shows the full month-by-month breakdown, including how the interest-to-principal ratio shifts over time.
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