How to Calculate a House Payment on a \$300,000 Loan

Divide your loan’s annual interest rate by 12 to determine your monthly rate. For example, if your loan has a 7.5 percent interest rate, divide 7.5 percent, or 0.075, by 12 to get a monthly rate of 0.00625.

Multiply your loan term in years by 12 to determine the number of monthly payments. In this example, assume you have a 30-year mortgage. Multiply 30 by 12 to get 360 monthly payments.

Add 1 to your monthly rate. Raise your result by an exponent equal to the total number of monthly payments. In this example, add 1 to 0.00625 to get 1.00625. Raise 1.00625 to the 360th power to get 9.4215.

Multiply your result by your monthly rate. In this example, multiply 9.4215 by 0.00625 to get 0.05888.

Subtract 1 from your Step 3 result. In this example, subtract 1 from 9.4215 to get 8.4215.

Divide your Step 4 result by your Step 5 result. Multiply that result by your \$300,000 loan amount to calculate your monthly principal and interest loan payment. In this example, divide 0.05888 by 8.4215 to get 0.00699. Multiply 0.00699 by \$300,000 to get \$2,097.