About this site
An independent mortgage calculator that shows the whole payment — principal, interest, county taxes, insurance and mortgage insurance — and names the source of every number.
Last reviewed Oct 25 2026
Maintained by bigbenben, Independent developer — corrections and questions: contact@mortmath.com
What this is
US Mortgage Calculator is an independent calculator, not a lender, broker or lead-generation site. It estimates a monthly PITI payment for any U.S. state and county, and shows the amortization schedule behind it.
Most mortgage calculators stop at principal and interest. Property tax, homeowners insurance and mortgage insurance are usually the larger surprise, and they change from one county to the next — which is why the county matters here, not just the state.
Who runs it
One person: bigbenben, an independent developer. I write the arithmetic, check the county rows against the Census tables, and keep the rate feed honest.
There is no company behind the site, no lender affiliation, no ads and no lead generation. It is not financial advice; the terms page says what the numbers are, and are not, for.
How the numbers are made
Every figure is arithmetic on a published input: Freddie Mac's PMMS rate survey, Census ACS county tax and home-value estimates, Fannie Mae's LLPA matrix, HUD's FHA tables, the VA funding fee statute and NAIC insurance averages.
The methodology page lists each source with the date of the figure behind it, and separates what is exact from what is estimated.
Corrections
If a number here is wrong, the site is wrong. Email with the page URL and what you expected; corrections are made in place, and the reviewed date at the foot of the page moves with them.