Home / Guides
Guides
Short guides that explain the numbers behind the calculators — what a mortgage payment is made of, how much house your income buys, and when refinancing pays.
- How Mortgage Payments Work — Principal, interest, taxes, insurance and PMI — what each part is, and why the split changes every month.
- How Much House Can I Afford? — The 28/36 rule worked out on an $80,000 salary, and what to do when the answer is less than you hoped.
- Refinance: When Does It Pay? — Break-even months, the trap of a longer term, and the questions to ask before you refinance.
Each guide uses the same worked examples as the calculators, so the numbers match. Rates in examples are examples only, not live market rates.
Sources and method. Standard amortization formula: monthly rate r = annual rate / 12, n = years × 12, payment M = P × r × (1+r)n / ((1+r)n − 1). PMI usually ends when the loan balance reaches 80% of the home value (Consumer Financial Protection Bureau guidance). Affordability uses the 28/36 rule of thumb used by many lenders. Rates in examples are examples only, not live market rates. Results are estimates, not financial advice.
Estimate, not financial advice. This calculator uses the standard amortization formula and the numbers you type in. It is not a loan offer and not financial advice. A lender will check your credit, income and debts and quote its own rate and fees before you borrow.