What is the formula to calculate EMI on loan amount?

The formula for Equated Monthly Installment (EMI) is:

A = P \frac {r(1+r)^n}{(1+r)^n-1}

where 'P' is the prinicpal amount borrowed, 'n' is the number of payment periods, and 'r' is the interest rate per time period expressed as a decimal. For example to caculate the monthly payment amount for a 30-year fixed mortgage at 4%, n = 30 x 12 = 360 months and r=0.04/12 = 0.00333.