Mortgage Payment Factors: Calculate Principal and Interest

A mortgage payment factor tells you the periodic principal-and-interest payment per stated amount borrowed. Read the factor’s units before multiplying. A decimal in one practice question is not a universal number for every loan.

Why the factor changes

For a fully amortizing fixed-rate mortgage, the payment calculation depends on the loan amount, interest rate, and repayment term. A table or supplied factor packages that calculation for a particular rate, term, and payment frequency. Use the factor supplied in the exercise, or the correct row and column of its table. See the CFPB explanation of monthly mortgage payments.

Worked example: two ways to state the same factor

An original practice exercise supplies a loan amount of $240,000 and a monthly payment factor of 0.006 per dollar borrowed.

$240,000 × 0.006 = $1,440 monthly principal and interest.

If the same factor is stated as $6 per $1,000 borrowed, calculate ($240,000 ÷ 1,000) × $6 = 240 × $6 = $1,440. Multiplying $240,000 directly by 6 would make the answer 1,000 times too large.

Principal and interest is not the entire housing expense

If this example separately gives annual property taxes of $3,600 and annual property insurance of $1,200, the monthly amounts are $300 and $100. PITI is $1,440 + $300 + $100 = $1,840.

Mortgage insurance and association dues may also affect total housing expense. Add each item only once and follow what the question asks for. See Mortgage Qualification: HER vs. TOR and PITI.

Do I need to memorize the factor?

Focus on using a supplied factor correctly. Do not memorize one decimal and reuse it for a different loan. If a practice problem requires a table and you cannot find it, send support the full permitted practice problem and its table or instructions.

A payment factor is also different from an annual interest rate. Loan balance × annual rate ÷ 12 gives a monthly interest calculation under that simplified convention; it does not calculate a fully amortizing principal-and-interest payment.

Try three practice questions

1. A question gives a $180,000 loan and a monthly factor of $6.50 per $1,000. What is monthly principal and interest?
2. A $200,000 loan uses a supplied monthly factor of 0.0055 per dollar. What is monthly principal and interest?
3. Monthly principal and interest is $1,100. Annual property taxes are $2,400 and annual property insurance is $1,200. What is PITI?

Answers and explanations

1. $1,170. 180 × $6.50.
2. $1,100. $200,000 × 0.0055.
3. $1,400. $1,100 + $200 + $100. These exercises use supplied hypothetical factors.

Keep studying

Review how to choose a math formula. Return to the exam-prep guide.

Submit a support request with your course, lesson or practice-question number, and the step you want explained. These are original study exercises, not recalled state-exam questions.