Data & Methodology

Every number on this site traces to a public primary source and a documented computation. This page describes both, so you can check our work.

Data sources

  • Mortgage rates: the Freddie Mac Primary Mortgage Market Survey (PMMS), retrieved through the Federal Reserve Economic Data (FRED) API. Series MORTGAGE30US (30-year fixed) and MORTGAGE15US (15-year fixed). PMMS is the standard weekly benchmark for U.S. average mortgage rates.
  • State median home values: the Zillow Home Value Index (ZHVI) for each state, refreshed as Zillow publishes new observations.
  • State property tax rates and program details: compiled from state revenue departments and housing authorities, reviewed when states publish updates.

Update cadence

  • Freddie Mac releases the weekly survey on Thursdays. Our pipeline ingests the new figures the same day, republishes the rate history, refreshes all 50 state calculators, and publishes that week's rate update automatically.
  • The current-rate figure shown in the calculator refreshes on weekdays.
  • Every page displays the effective date of the data it shows, and our sitemap reports the true last-modified date of each page. We never bump dates without a content change.

How figures are computed

  • Monthly principal & interest: the standard amortization formula, P × r(1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is the loan amount, r the monthly rate, and n the number of payments. The calculator adds property tax, insurance, PMI, and HOA on top when you provide them.
  • "Typical payment" examples (weekly updates, state pages) assume the median-priced home for the geography, 20% down, and a 30-year term at that week's PMMS average. The assumptions are stated next to every example.
  • 52-week highs, lows, and changes are computed directly from the PMMS series; no smoothing or adjustment.

Corrections

If a data error is found, we correct the affected pages by re-rendering them from the source series and note material corrections on the page. Because pages are generated from the source data rather than edited by hand, a correction at the source propagates everywhere it appears.

Independence

Rate data and calculations are independent of advertising. Lender offers that appear on some pages come from our advertising partner, are always labeled, and have no influence on the rates, history, or calculations we publish. The calculator itself is free, requires no signup, and stores your inputs only in your own browser.

Questions about the data? Contact us. Quick Mortgage Calculator is owned and operated by Pockadot LLC.