Estimate your full monthly housing payment — principal, interest, property tax, and insurance.
Enter the home price and your planned down payment, plus the interest rate and term, and the calculator computes the classic principal-and-interest payment using the standard amortisation formula. Add your estimated annual property tax and home insurance and it produces the more realistic PITI figure — the total that actually leaves your bank account each month.
Lenders qualify you on this full housing cost, not just principal and interest, so budgeting from PITI avoids the most common first-time-buyer surprise: a payment several hundred dollars higher than the number in the mortgage advert.
A $350,000 home with $70,000 down (20%) leaves a $280,000 loan. At 7% over 30 years, principal and interest come to about $1,863/month. Add $3,500/year of property tax ($292/mo) and $1,200/year of insurance ($100/mo) and the real monthly cost is roughly $2,255. Over the full term you would pay about $390,000 in interest alone — more than the original loan.
Not as separate fields. If you expect PMI (usually required below 20% down in the US) or HOA dues, add their annual cost into the insurance field to fold them into the monthly total.
Use the price you realistically expect to pay. If you're early in the search, run the calculator at a few price points to see how sensitive the payment is — it's an excellent way to set your own ceiling before falling in love with a house.
Interest accrues on the outstanding balance every month for 360 months, and in the early years the balance barely moves. That is normal amortisation, not a trick — but it is also why extra principal payments early in the loan are so powerful.