Calculator Basics

    Calculator Basics · Sources

    Data Sources

    Every figure on a citable page links back to a named primary source with a publication or refresh date — Census home values and tax rates, Freddie Mac PMMS rates, and federal program fee schedules.

    Editorial policy · CalculatorBasics.com · Last updated 2026-08-24

    By Dexter UmelFounder

    Primary sources

    SourceUsed forRefresh cadence
    U.S. Census Bureau ACS 2023 (5-Year Estimates)Median home values and effective property tax rates by stateAnnually (when ACS release updates)
    Freddie Mac PMMS via FRED MORTGAGE30US30-year fixed mortgage rate anchorWeekly (Thursday PMMS release)
    HUD Mortgagee Letters (e.g., ML 2023-05)FHA upfront and annual MIP scheduleWhen HUD publishes letter updates
    38 CFR 36.4313VA funding fee ratesWhen VA publishes schedule updates
    USDA RD Instruction 3555USDA upfront and annual guarantee feesWhen USDA publishes instruction updates
    IRS Rev. Proc. 2025-322026 federal income tax bracketsAnnually (tax year)

    How sources appear on pages

    Research pages include a mono-typed source line with the rate or dataset vintage. Methodology pages cite the governing document for each fee or formula. Calculator results link to Methodology for full formulas.

    Verification

    Mortgage and refinance calculator outputs are checked against a 12-scenario verification matrix documented at /methodology/verification-2026-08.