Question: what is the formula for calculating a 30 year mortgage?
Answer: Fixed-rate mortgage payments stay the same for the life of the loan. Example: $500,000 mortgage loan at 5 percent interest for 30 years making 12 payments a year -- one per month. Multiply 30 -- the number of years of the loan -- by the number of payments you make each year. For example, 30 X 12 = 360.