How to Calculate Your Monthly Mortgage Payment
The monthly mortgage payment comes down to four variables: your loan amount (home price minus down payment), your annual interest rate, your loan term (15 or 30 years), and whether you pay PMI. Our mortgage calculator handles all of this — enter your numbers and get your monthly payment, total interest, and a full amortization schedule instantly.
The Standard Mortgage Formula:
M = P × [r(1+r)ⁿ] / [(1+r)ⁿ−1]
P = loan amount, r = monthly rate, n = total payments
15-Year vs 30-Year Mortgage: The Real Cost Difference
The choice between 15 and 30 years is the single most impactful decision in your mortgage. The savings are enormous — but so is the monthly difference.
| $350,000 Loan at 7% | Monthly Payment | Total Interest | Total Cost |
|---|---|---|---|
| 30-Year Fixed | $2,329/mo | $488,000 | $838,000 |
| 15-Year Fixed | $3,145/mo | $216,000 | $566,000 |
| 15-Year Saves You | −$816/mo more | Save $272,000 | $272,000 less |
How Much House Can I Afford in 2026?
The industry-standard 28/36 affordability rule: your total housing costs should be under 28% of gross monthly income, and total debt under 36%. For a $90,000/year household ($7,500/month): maximum mortgage + taxes + insurance = $2,100/month. At 7% over 30 years, that supports roughly a $315,000 loan. Add your down payment to find your maximum home price.
Use our mortgage calculator to reverse-engineer this: try different home prices until the monthly payment hits your 28% ceiling. That is your true home affordability number — not what a lender offers, but what you can comfortably sustain.