How to Calculate Your Mortgage Payment
A complete guide to understanding mortgage calculations and what factors affect your monthly payment
Understanding how mortgage payments are calculated can help you make smarter decisions when buying a home. In this guide, we'll break down the math behind your monthly payment and show you what factors have the biggest impact.
The Basic Mortgage Formula
Your monthly mortgage payment is calculated using this formula:
M = P × [r(1+r)^n] / [(1+r)^n – 1]
Where:
- M = Monthly payment
- P = Principal loan amount
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (years × 12)
Don't worry if that looks complicated—that's why we built our Mortgage Calculator to do the math for you!
What Affects Your Payment?
1. Loan Amount (Principal)
The more you borrow, the higher your payment. A $300,000 loan will have payments roughly double that of a $150,000 loan, all else being equal.
2. Interest Rate
Even small changes in interest rates can have a big impact. On a $300,000 loan:
- At 6%: $1,799/month
- At 7%: $1,996/month
- At 8%: $2,201/month
That's over $400/month difference between 6% and 8%!
3. Loan Term
A 30-year loan has lower monthly payments than a 15-year loan, but you'll pay much more in total interest.
| Term | Monthly Payment (on $300K at 7%) | Total Interest Paid |
|------|----------------------------------|---------------------|
| 30 years | $1,996 | $418,527 |
| 15 years | $2,696 | $185,367 |
4. Property Taxes and Insurance
Your total monthly payment (often called PITI) includes:
- Principal
- Interest
- Taxes
- Insurance
Our calculator includes all of these to give you the full picture.
Tips for Lower Payments
1. Improve your credit score before applying—better scores mean lower rates
2. Make a larger down payment to reduce the loan amount
3. Shop around for the best interest rate
4. Consider paying points to buy down your rate if you'll stay in the home long-term
Ready to Calculate?
Use our free Mortgage Calculator to see exactly what your monthly payment would be. You can adjust the loan amount, interest rate, and term to compare differentAll Articles