India, Oct. 10 -- You use an EMI calculator to find out what a loan will cost each month, and then the lender's offer shows a different EMI. The gap is frustrating, but it almost always has a simple cause: one of the numbers you entered was not the one the lender used.

The calculator gives you the right answer every time if you enter the lender's own figures: the full loan amount, the interest rate offered to you and the tenure counted in months. Take most care with the rate: one point too low barely changes the EMI, but on a Rs. 2,50,000 loan it hides over Rs. 4,000 of interest.

Why an EMI calculator shows a different EMI from your loan offer

An EMI calculator and a lender both work out your EMI with the same reducing-balance formula,...