ReviewedEducational article · Updated Oct 2026
Key takeaways
- A fixed EMI keeps the payment constant while the interest/principal split shifts each month.
- Early payments are mostly interest; later payments are mostly principal.
- The EMI formula comes from setting the present value of all payments equal to the loan amount.
- Amortisation schedules make the shift visible month by month.
EMI stands for equated monthly instalment: a fixed payment you make each month so that a loan is fully repaid over a set term. The payment stays the same, but what it is made of does not. Understanding that split is the key to reading any amortisation schedule.
Why the split changes
Each month, interest is charged on the remaining principal. Early on, the balance is large, so interest is large — and most of your EMI goes to interest. As the principal shrinks, interest shrinks too, so more of the same EMI chips away at principal.
Your payment does not change. The job it does each month does.
That is why the first years of a long mortgage feel like you are barely making a dent — you are, but mostly in interest, not in the balance on the statement.
Equated monthly instalment: one payment sized so that principal and interest together clear the loan exactly by the final month.
The EMI formula
For a fixed-rate loan with monthly payments:
EMI = P · r · (1+r)n / ((1+r)n − 1)
- P — the loan principal
- r — the monthly interest rate (annual rate ÷ 12)
- n — the number of months in the term
When the rate is zero, the formula collapses to a simple P / n. The formula is derived by requiring that the present value of all future EMIs equals the amount borrowed today.
A small worked example
Imagine a $12,000 loan at 12% per year for 12 months. The monthly rate is 1%. The EMI works out to about $1,066.
- Month 1 interest ≈ $120; principal ≈ $946; balance ≈ $11,054.
- Month 6 interest ≈ $62; principal ≈ $1,004.
- Month 12 interest ≈ $10; principal ≈ $1,056 — and the loan is gone.
Same $1,066 each month. Completely different interest/principal mix.
Reading an amortisation table
A full schedule lists every month: opening balance, interest, principal, payment and closing balance. It is the same arithmetic repeated: interest = balance × monthly rate; principal = EMI − interest; new balance = old balance − principal. Rounding can make the final payment a few cents different — lenders handle that with a small adjustment on the last instalment.
Prepayment insight: because early interest is high, any extra payment applied to principal early removes interest that would have been charged for the rest of the term. That is the math behind “extra mortgage payments” articles — and behind our Mortgage Payoff calculator.
What the model leaves out
Real loans can include fees, insurance, variable rates, payment holidays and penalties. An educational EMI calculator shows the clean fixed-rate path so you can see the structure clearly before comparing real product disclosures.
This article is for general educational purposes only and is not financial advice. Examples use simplified, hypothetical numbers and ignore taxes, fees and personal circumstances. Consider speaking with a qualified professional before making financial decisions. See our full disclaimer.