MORTGAGE PAYMENT
About this calculator
This mortgage calculator computes the monthly principal and interest payment on a fixed-rate home loan. Enter the loan amount, interest rate, and term in years. The calculator does not include property tax, homeowner's insurance, PMI, or HOA — those are typically escrowed and added on top. To estimate total housing cost, add roughly 1.5–3% of home value annually for those items, divided by 12.
How to use this calculator
Enter your loan amount (the amount you're borrowing — purchase price minus down payment), the annual interest rate as a percentage (e.g., 6.5), and the loan term in years. The calculator returns the monthly principal and interest (P&I) payment plus the total amount paid over the life of the loan and the total interest cost.
For a complete monthly housing payment (PITI — principal, interest, taxes, insurance), add roughly $200–$500 per month for property tax, $80–$200 for homeowner's insurance, and $50–$150 for PMI if your down payment is under 20%. HOA dues, if applicable, also add to PITI but aren't part of the loan itself.
Worked example
$300,000 loan at 6.5% for 30 years:
Monthly P&I = $1,896.20. Total paid over 30 years = $682,633. Total interest paid = $382,633 — more than the original loan amount.
Same loan at 15 years: Monthly P&I = $2,613. Total paid = $470,388. Total interest = $170,388.
The 15-year payment is $717/month higher but saves $212,245 in interest over the life of the loan. That tradeoff — pay more in monthly outflow over 15 years to save $212K in interest — only makes sense if you'd otherwise actually invest the difference at a return higher than the mortgage rate (after tax) and have the income stability to support the higher payment for 180 straight months.
Common mistakes & waste factors
Confusing rate (APR) with monthly rate. The calculator handles the conversion (rate ÷ 12) internally — always enter the annual percentage as a percentage, not a decimal. 6.5%, not 0.065.
Forgetting taxes, insurance, and PMI when comparing affordability. P&I on a $300K loan looks like $1,896/month, but the true PITI is closer to $2,400–$2,800. Lenders typically cap your total housing cost at 28–31% of gross income — using P&I alone can put you 30% over what you can actually qualify for.
Choosing a long term to lower the payment without considering the interest cost. Going from 15 to 30 years roughly doubles your total interest payment.
Ignoring the impact of small rate changes. A 1% rate increase on a $400K loan adds roughly $250–$300 per month — that's $90–$108K over 30 years.
Rules of thumb
Quick monthly P&I estimate: $6 per $1,000 borrowed at 6% for 30 years. So $300K = ~$1,800/month, $400K = ~$2,400/month. Adjust ±$60 per $1,000 for each 1% rate change.
Total interest paid on a 30-year loan at 6–7% rates ≈ the loan amount itself. At 4%, total interest is closer to ½ the loan; at 8%, it's about 1.4×.
Bi-weekly payments (paying half your monthly amount every two weeks) shave about 5–7 years off a 30-year mortgage and save 20–25% of total interest, because you make 13 monthly payments per year instead of 12.
PITI typically runs 25–35% above the P&I number on this calculator. Use the higher figure for affordability planning, not P&I alone.
Refinancing rule of thumb: a 0.75–1% rate drop is usually enough to justify closing costs if you'll stay in the home 3+ more years.