Best Home Buying Tools — 10 Free Calculators for Every Step of the Process

The 28/36 rule is the standard starting framework: total housing costs (mortgage P+I, property taxes, insurance, PMI, and HOA) should not exceed 28% of gross monthly income, and all debt obligations combined should not exceed 36%. On an $80,000 gross annual salary ($6,667/month), the 28% ceiling allows approximately $1,867/month in total housing costs. At 7% interest with 10% down and typical tax and insurance rates, that payment supports a purchase price of approximately $210,000–$230,000. The House Affordability Calculator gives a precise figure based on your actual income, debts, down payment, and local property tax rate.

A complete mortgage payment has four components, often abbreviated PITI: Principal (the portion reducing your loan balance), Interest (the cost of borrowing), Taxes (property taxes, typically escrowed and paid monthly as 1/12 of the annual tax bill), and Insurance (homeowners insurance, also escrowed). If your down payment is below 20%, Private Mortgage Insurance (PMI) is also required, typically 0.5–1.5% of the loan amount annually. For a $400,000 home with 10% down in a 1.5% tax jurisdiction, PITI plus PMI is often $700–$900/month more than the principal and interest alone — a difference that matters significantly for affordability calculations.

The 20% threshold eliminates PMI and reduces total interest paid over 30 years. But the extra cash has a real opportunity cost — $40,000 in an investment account growing at 7% annually becomes approximately $157,000 over 30 years. In appreciating markets, buying sooner with 10% down often captures more in home price appreciation than you'd pay in PMI over the years it takes to save the extra 10%. The right answer depends on your market's appreciation rate, your savings timeline, your ability to invest the difference, and how long you plan to stay in the home. The Down Payment Calculator models all of these scenarios explicitly.

FHA loans are government-backed and designed for buyers with lower credit scores (580 minimum for 3.5% down) or limited down payment savings. They allow higher DTI ratios but require a 1.75% upfront MIP and ongoing annual MIP — which for loans with less than 10% down persists for the life of the loan, not just until 20% equity. Conventional loans have stricter credit requirements (typically 620 minimum, best rates at 740+) but PMI cancels automatically at 78% LTV. For buyers with strong credit and a 10%+ down payment, conventional loans are usually less expensive total. For lower credit scores or smaller down payments, FHA is often the only viable path. The FHA Loan Calculator compares both for your specific situation.

The price-to-rent ratio (median home price divided by median annual rent) is the standard market-level indicator: below 15 generally favors buying; above 20 generally favors renting; between 15–20 is market-dependent. But this ratio alone is incomplete. You also need: your time horizon (transaction costs require at least 5–7 years to recover), expected local appreciation, property tax rates, your alternative use of the down payment, and rent inflation trends. The Rent vs. Buy Calculator models all of these variables and shows the break-even year — the point at which buying becomes the better financial decision — for your specific numbers.

Extra principal payments produce compounding interest savings because each dollar paid early reduces the principal on which future interest is calculated. On a $350,000 30-year mortgage at 7%, an extra $100/month saves approximately $36,000 in interest and pays off 3.5 years early. An extra $300/month saves over $93,000 and pays off 8 years early. An extra $500/month saves over $130,000 and pays off 11 years early. The Mortgage Payoff Calculator models any payment scenario, including lump-sum extra payments and biweekly payment structures, so you can see the exact savings from any approach.