These two show up in the same conversations (loans, savings, “how does interest work”) often enough that it’s easy to blur them together. They’re actually solving opposite problems.
Compound interest: money growing
Compound interest describes what happens when interest earned in one period gets added to the principal, so the next period’s interest is calculated on a larger base. It’s the mechanism behind savings accounts, investments, and the (often quoted) “interest on interest” effect. The formula is straightforward: A = P × (1 + r/n)^(n×t), where P is your starting amount, r is the annual rate, n is how often it compounds per year, and t is time in years.
Example: $10,000 at 6% annual interest, compounded monthly, for 5 years grows to roughly $13,489, a gain of about $3,489 with no further contributions.
EMI: debt shrinking
EMI (Equated Monthly Installment) describes the opposite situation: you owe a lump sum (a loan) and pay it back in fixed monthly amounts that include both principal and interest. Each payment is the same size, but the mix shifts over time, early payments are mostly interest, later payments are mostly principal, because the loan balance (and therefore the interest charged on it) shrinks with every payment. The formula is 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 monthly payments.
Example: a $10,000 loan at 6% annual interest (0.5% monthly) over 5 years (60 months) has a fixed EMI of about $193.33/month, totaling roughly $11,600 paid back, about $1,600 in interest.
The actual difference
Compound interest answers “how much will my money grow.” EMI answers “how much will I pay to pay off a debt.” They use similar-looking exponential math because both involve interest applied repeatedly over time, but one is calculating growth on money you keep, the other is calculating repayment on money you owe.
Projecting savings growth? Use our Compound Interest Calculator. Working out a loan payment? Use the EMI Loan Calculator.
Frequently Asked Questions
What is the difference between EMI and compound interest?
Compound interest shows how saved money grows as interest is added to the balance. EMI is the fixed monthly payment that pays off a loan, interest included.
How is interest calculated in an EMI loan?
On a reducing balance: each month’s interest is charged on the loan amount still outstanding, so the interest part of each payment falls over time while the principal part rises.
Why are early EMI payments mostly interest?
Because the outstanding balance is largest at the start of the loan. As the balance shrinks, less of each fixed payment goes to interest and more goes to principal.