General Approach
Calculators run client-side in your browser and use the values you enter plus any defaults shown on the page. Results are rounded for display, so small differences from lender systems can occur.
Mortgage Payment
For a fixed-rate amortizing loan, principal and interest use the standard payment formula M = P[r(1+r)^n] / [(1+r)^n - 1], where P is principal, r is the monthly interest rate, and n is the number of monthly payments. Taxes, insurance, HOA dues, and mortgage insurance are added separately when entered.
Debt-to-Income Ratio
DTI uses gross monthly income. Front-end DTI divides proposed housing obligations by gross income. Back-end DTI adds the recurring debts entered by the user. Displayed ranges are educational reference bands, not approval decisions.
Home Budget Stress Test
The affordability budget tool uses take-home pay rather than gross underwriting income. It subtracts housing costs, living expenses, and the savings target entered by the user to estimate a monthly cash buffer. It is intentionally separate from lender-style DTI.
PMI and FHA MIP
PMI examples use an annual insurance-rate assumption applied to the loan balance for illustration. Actual PMI is priced by the insurer/lender. FHA mortgage-insurance rules depend on loan characteristics and origination rules, so articles link to HUD guidance rather than treating one example as universal.
Rent vs. Buy
The rent-vs-buy model includes rent growth, down payment, mortgage amortization, property-tax rate, homeowners insurance, HOA fees, a maintenance reserve, buying closing costs, selling costs, home appreciation, and the hypothetical return on investing the down-payment cash. The comparison is a scenario model and is highly sensitive to assumptions.
Refinance Break-Even
The simple payment break-even is estimated closing costs divided by estimated monthly principal-and-interest savings. It does not by itself determine whether refinancing is beneficial because loan-term resets, points, lender credits, taxes, escrow changes, financed costs, and opportunity cost can matter.
Closing Costs
The closing-cost calculator combines editable inputs with clearly identified example defaults. Official Loan Estimates and Closing Disclosures are the authoritative transaction documents.
Privacy of Calculator Inputs
Core calculations are performed in the browser. Built-in share controls are configured to share the calculator page without appending the financial inputs to the URL.