Methodology
Every estimate should show its work.
The calculator is intentionally conservative where reality is uncertain and explicit about source resolution where local data is modeled.
How we calculate it
- Principal and interest
- Standard fixed-rate annuity formula, with inverse solving for payment-budget mode.
- House Poorness Index
- Take-home income minus true housing cost, debts, and a household-size baseline non-housing budget.
- True housing cost
- Loan payment (principal and interest), property tax, home insurance, mortgage insurance, HOA or condo fees, maintenance, and utilities.
- Upkeep, utilities & HOA
- Maintenance uses the standard rule of thumb — 1% of the home's value per year, divided across twelve months. It's a planning estimate, not a quote; older homes typically run higher. Utilities are a flat monthly estimate, one of only two placeholder values left in this calculator (the other is the household baseline spending amount below). HOA or condo fees are simply whatever you enter. None of the three are required by a lender to qualify you for a loan — a lender's math skips maintenance and utilities entirely — and that gap between what a lender counts and what a home actually costs to live in is the reason this calculator exists.
- Closing costs
- Ranges for lender fees, title and settlement, transfer taxes, recording, and prepaid taxes and insurance.
Where the data comes from
- Property tax rate
- US Census American Community Survey — median real estate taxes paid divided by median home value, measured at the county level. We fetch this for every county in the United States in one build-time pull, so any ZIP resolves to a real county rate. ZIP-to-county mapping uses the Census 2020 ZCTA-to-county relationship file; when a ZIP straddles more than one county we use the county covering the largest share of its area and say so. Some counties are top-coded by the Census (taxes capped at $10,000 or more, home value at $2,000,000 or more); where that happens we flag the rate as approximate instead of implying false precision.
- Home insurance
- NAIC Homeowners Insurance Report 2022 state average premium for the standard HO-3 owner-occupied policy, published through the Insurance Information Institute, for all 50 states and DC. We take the real state average as the midpoint and model a low-to-high range around it — so the base number is real and the spread is modeled. Every county then gets a local risk multiplier built from the FEMA National Risk Index: we add up the expected annual building loss from the perils a standard policy actually covers — hurricane and straight-line wind, hail, tornado, wildfire, and winter storms — as a share of the county's building value, then normalize within each state so the state's average premium is redistributed across its counties, not inflated. Flood and earthquake are deliberately left out of this multiplier, because a standard policy excludes them; we surface them as risk flags instead. Because a pricier home costs more to insure, we scale the premium with home price: we divide the state's average premium (times the county multiplier) by that state's median home value (US Census ACS) to get a rate per dollar, so exploring a higher price raises the insurance line and a lower one drops it. Honest caveat: this is an approximation. Insurance covers the cost to rebuild, not the land underneath — so in expensive-land areas (think coastal California) a real quote grows more slowly than the price. If you have an actual quote, type it into “Fine-tune local costs” and we’ll use your fixed dollar figure instead of the scaled estimate.
- Risk flags
- Up to three plain-language flags per county come from the FEMA National Risk Index county hazard ratings, shown when a hazard rates Relatively High or Very High. Covered perils (hurricane and wind, hail, tornado, wildfire, winter storms) are phrased as premium pressure, since they are already baked into the insurance multiplier. Flood and earthquake are called out separately with a warning that a standard homeowners policy does not cover them — flood needs its own policy and depends on the address's flood zone, and earthquake coverage is a separate add-on. Flags are sorted so the most severe risks show first.
- Mortgage rates
- Freddie Mac Primary Mortgage Market Survey weekly averages for the 30-year and 15-year fixed loan, fetched live from the Federal Reserve (FRED) and cached for about a day.
- State income tax
- State income tax comes from the Tax Foundation's “State Individual Income Tax Rates and Brackets, 2026” table (rates as of February 11, 2026). For all 50 states and DC we model an effective rate — tax owed divided by gross income — at a range of incomes for both single and married-filing-jointly filers, applying each state's own tax brackets, standard deduction, and personal exemption, so the estimate rises with income and shifts with filing status. The nine no-income-tax states show zero; Washington's capital-gains tax is left out because it does not apply to wages. Honest caveats: this is modeled from the published brackets and does not account for tax credits (or their phase-outs), local income taxes (such as New York City, Maryland counties, and Ohio cities), or the way retirement contributions and other deductions interact with state rules. Treat it as a close estimate, not a filed return.
- Closing costs
- We research the tax a home sale triggers when the deed changes hands — sometimes called a transfer tax, conveyance tax, deed tax, or recordation tax depending on the state — for every state, plus the cities and counties that charge their own on top: New York City, Philadelphia, Chicago, San Francisco, Baltimore, Washington D.C., and more. Many states charge one flat rate; some (Washington, Connecticut, Hawaii, Vermont, New Jersey, New York, D.C.) step the rate up as the price climbs. Who customarily pays — the buyer, the seller, or a 50/50 split — varies by state and is baked into each entry, so the number in your closing-cost total only ever counts the buyer's customary share; the rest shows up as a note so it's never quietly dropped or quietly billed to the wrong side. Title insurance (the policy that protects against a defect in the property's ownership history) follows the same two-track approach as other estimates here: Texas, Florida, and New Mexico set their premiums by law, so we run their exact published rate tables; every other state leaves rates to competition, so we use a nationwide curve built from published cost studies that declines as a share of price the more expensive the home is. Transfer-tax research: researched 2026-07. Title-insurance research: researched 2026-07.
- Still placeholders
- Utilities and the household baseline non-housing budget are not yet sourced. They are reasonable stand-ins, labeled as placeholders, until real data is wired in. (State income tax is no longer a placeholder — see above.)
Curated Example ZIPs
Property tax covers every US county and insurance covers every state; the ZIPs below are hand-curated examples that also carry local risk flags.
| ZIP | Property Tax | Insurance | Baseline |
|---|---|---|---|
| 94110San Francisco, CA | 0.76%*Census ACS · ACS 2024 1-year | $1,120/yrNAIC state average 2022 · FEMA NRI December 2025, range modeled | $4,700/moPlaceholder — not yet sourced |
| 07030Hoboken, NJ | 1.69%Census ACS · ACS 2024 1-year | $1,060/yrNAIC state average 2022 · FEMA NRI December 2025, range modeled | $4,550/moPlaceholder — not yet sourced |
| 33139Miami Beach, FL | 0.76%Census ACS · ACS 2024 1-year | $2,310/yrNAIC state average 2022 · FEMA NRI December 2025, range modeled | $4,200/moPlaceholder — not yet sourced |
| 75201Dallas, TX | 1.41%Census ACS · ACS 2024 1-year | $2,400/yrNAIC state average 2022 · FEMA NRI December 2025, range modeled | $4,050/moPlaceholder — not yet sourced |
| 80202Denver, CO | 0.48%Census ACS · ACS 2024 1-year | $2,260/yrNAIC state average 2022 · FEMA NRI December 2025, range modeled | $4,350/moPlaceholder — not yet sourced |
| 98103Seattle, WA | 0.82%Census ACS · ACS 2024 1-year | $860/yrNAIC state average 2022 · FEMA NRI December 2025, range modeled | $4,500/moPlaceholder — not yet sourced |
* Property tax rate is approximate because a Census median for this county is top-coded.