For example, if you borrow Rs. 10,000 at an annual interest rate of 6% for 3 years (36 months), the monthly EMI would be EMI = 10,000 (0.06/12) (1 + 0.06/12)^36 / ((1 + 0.06/12)^36 - 1) = Rs. 303.87.
If you prepay your mortgage you reduce the principal balance, reducing the interest due next month and every month forward. If you prepay $1000 on your mortgage, the interest next month will be reduced by 10003.7%/12=3.08 You will still make the same payment, but an additional 3.083 will be credited toward principal.
Fortunately, Excel can be used to create an amortization schedule. The amortization schedule template below can be used for a variable number of periods, as well as extra payments and variable interest rates.