How EMI Works — Principal, Interest & Tenure Explained

What is an EMI?

An Equated Monthly Instalment (EMI) is the fixed amount you pay your lender every month until your loan is fully repaid. It is “equated” because the amount stays the same throughout the loan term — even though the split between principal and interest changes every month.

Every EMI you pay does two things at once:

1. Pays off interest — the cost of borrowing money
2. Reduces the principal — the actual amount you borrowed

In the early months of a loan, most of your EMI goes toward interest. As time passes, more of each payment chips away at the principal. This is called amortization.

The Formula Behind EMI

Banks and lenders use the PMT (Payment) formula from finance:

EMI = P × r × (1+r)^n / ((1+r)^n − 1)

Example:
  Loan: ₹5,00,000 @ 8.5%/yr, 5 years
  r = 8.5 / 12 / 100 = 0.007083
  n = 60
  EMI = 5,00,000 × 0.007083 × (1.007083)^60 / ((1.007083)^60 − 1)
      = ₹10,248

  Total payment  = ₹10,248 × 60 = ₹6,14,902
  Total interest = ₹6,14,902 − ₹5,00,000 = ₹1,14,902

def emi(p, annual_rate, months):
    r = annual_rate / 12 / 100
    return p * r * (1+r)**months / ((1+r)**months - 1)

print(emi(500000, 8.5, 60))  # 10247.57

function emi(p, annualRate, months) {
  const r = annualRate / 12 / 100;
  return p * r * Math.pow(1+r, months) / (Math.pow(1+r, months) - 1);
}
console.log(emi(500000, 8.5, 60)); // 10247.57

How Tenure Affects Your EMI

Choosing a longer tenure lowers your monthly EMI but dramatically increases the total interest paid. Here’s the same ₹5,00,000 loan at 8.5% across different tenures:

A 20-year loan more than doubles the total cost compared to a 5-year loan. The lower monthly payment comes at a steep long-term price.

How Interest Rate Affects Your EMI

Even a 1% change in interest rate makes a meaningful difference over a long loan:

Fixed Rate vs Floating Rate

Fixed rate: Your interest rate and EMI stays the same throughout the loan. Predictable and easier to budget — you always know exactly what you owe each month.

Floating rate: The rate changes with market conditions (linked to the RBI repo rate). It can go up or down. Floating rates often start lower than fixed rates but carry uncertainty — your EMI could rise if rates increase.

Tips for Managing Your EMI

Calculate Your EMI Now

Use our free EMI Calculator to try different combinations of principal, rate, and tenure instantly. It shows your monthly EMI, total interest, and a breakdown of principal vs interest.