How this mortgage calculator works
U.S. homeowners rarely pay “just the mortgage.” Most conventional loans collect PITI each month: principal, interest, property tax, and homeowners insurance. If you put down less than 20%, private mortgage insurance (PMI) is usually added until you reach about 20% equity. Condos and planned communities may also bill HOA dues.
This tool uses the standard fixed-rate amortization formula for principal and interest, then layers the extras as monthly amounts. Property tax is estimated from a statewide average effective rate you can override. Insurance is a yearly premium divided by 12. PMI is modeled as an annual percentage of the loan balance divided by 12 — real PMI can be monthly or single-premium and varies by credit score and loan-to-value.
Change the down-payment chips to see PMI appear or disappear. That is often a larger jump than a 0.125% rate change.