About
HouseholdMath started with an argument about a condo.
A friend had bought a place in 2020 and mentioned the price. Someone did the mental arithmetic out loud — twenty percent down, whatever rates were then — and got a number that felt far too low. Everyone at the table had a different guess, and every guess was wrong, because none of them had accounted for the property tax, or the condo fee, or the mortgage insurance a smaller down payment would have triggered. The gap between the intuitive number and the real one was almost seven hundred dollars a month.
That gap is what this site closes.
What it does
Give it an address, a closing date and a price. It works out what the mortgage rate was that month, what the property tax rate is in that state, what insurance typically costs there, and whether mortgage insurance applies. It amortises the loan properly, tracks the home's likely value along the FHFA index for that state, and tells you where the equity stands. Then it runs the lender's ratio backwards to say what income that payment demands.
Every number names its source. Every assumption is editable. The whole thing runs in your browser and nothing is ever sent anywhere.
What it deliberately does not do
It does not tell you what your neighbour earns.
The optional salary estimate describes an occupation in a market — what a licensed electrician with twelve years in typically makes around Denver — using published wage percentiles. It has no idea who lives at the address, whether there are two incomes, whether there is family money, an inheritance, a pension, equity rolled over from a previous sale, or a business on the side. Anyone reading that number as a statement about a specific person has misread it, and the results page says so.
The number that is reliable is the one about the house: this address costs this much to hold, and holding it comfortably takes about this much income. That is a fact about a property, derived from public data, and it is the honest version of the question people are actually asking.
Who built it
One person, as a side project, because the arithmetic kept coming up and nothing on the internet did it properly in one place. Corrections are welcome — particularly on county tax rates and insurance markets, where state averages are the weakest link in the model.