How the mortgage payment calculator works
PITI: the four lines that own your month
Principal and interest come from the standard amortization formula; property taxes run 0.5–2.5% of value a year depending on state; insurance varies by hazard; and PMI (0.3–1.2% of the loan a year) applies below 20% down until equity crosses the line. Quote calculators show P&I because it is the only line they know — budget calculators show PITI because it is the only one your bank account notices.
Why the term matters more than it looks
At 6.5%, a 30-year loan on $357k costs about $2,257/mo in P&I; a 15-year costs $3,113 — but total interest drops from ~$455k to ~$103k. The term is the largest single lever on lifetime cost, and the monthly difference is smaller than most buyers fear.
Where to get the non-P&I numbers
Taxes: the county assessor's rate on the actual listing. Insurance: a real quote for the ZIP and build year. PMI: 0.3–1.2% of loan by credit score. Ten minutes of phone calls makes this calculator exact — and makes offers dramatically less speculative.