Complete Mortgage Calculator

Comprehensive mortgage and home buying calculator. Calculate monthly payment, affordability, closing costs, PMI, and compare 15 vs 30-year terms. Includes rent vs buy analysis, refinance calculator, and amortization schedule.

This is the multi-mode mortgage tool: Calculation Mode switches between four entirely different code paths (Payment, Affordability, Refinance, Rent vs Buy), and at the default Payment Calculator mode, the Refinance and Rent vs Buy sections — Refinance Savings, Refinance Breakeven, Buying Breakeven Year, Recommendation — are all gated behind a calculationMode check (lines 139, 156) and stay pinned at their zero-initialized values no matter what you enter in Current Loan Balance, Current Interest Rate, Current Monthly Payment, Monthly Rent, or any of the other refinance/rent-vs-buy fields; every one of those inputs measures exactly zero effect on every output while Payment Calculator mode is selected. The refinance branch's real gate is stricter than just switching modes, though: it is calculationMode === 2 AND currentLoanBalance > 0 (line 139) — since Current Loan Balance defaults to $0, switching Calculation Mode to "Should I Refinance?" alone is not enough to activate the refinance math; you also need a non-zero Current Loan Balance. Current Interest Rate is a step further than merely dormant in other modes: inputs.currentRate is never read anywhere in this engine at all (it is declared as an input and referenced only in the inertness claim below), so it has zero effect on every output in every mode, not just outside Refinance mode. PMI (Monthly PMI, PMI Required) is a genuine hard threshold, not a smooth curve: it switches on at 0.7% of the loan annually the instant Down Payment drops below 20%, and off entirely at 20% or above (line 90) — moving Down Payment from 22% to 18% around the default flips PMI from $0 to about $191/month, by far the largest swing any input produces on that output, purely because it crosses the threshold rather than because of a large underlying rate change. Down Payment moves Total Monthly Payment down by about 12% across a ±10% probe — a smaller share than Home Price's roughly 18% — a mix of the direct financed-amount reduction and, when it crosses the 20% line, the PMI switching off too. Annual Household Income never moves Total Monthly Payment, Monthly P&I, or any of the payment-calculation outputs — it's used only in the separate affordability math (Max Affordable Home, Max Monthly Payment), which the calculator runs unconditionally regardless of which mode is selected. This calculator does not account for mortgage points, an adjustable-rate structure, or state-specific PMI cancellation rules beyond the flat 20% equity line.