Plus the spread over the 10-year Treasury, delinquency and debt-service health, and the monthly payment on the typical US home at today's rate.
The daily figures are Optimal Blue's Mortgage Market Indices: the average rate on loans actually locked each business day, split by loan type, so they move the day the market moves. The weekly figure is Freddie Mac's survey of the rate lenders offer a well-qualified borrower on a conforming 30-year loan, published Thursday mornings and the number most news reports quote. The two usually sit within a few tenths of each other; when they diverge, it is because the daily index has already caught a move the weekly survey has not.
Mortgage rates follow the 10-year Treasury, not the fed funds rate, which is why a Fed cut can leave them unchanged or even higher: the spread between the two widens when lenders price in prepayment or credit risk and narrows when markets are calm. Jumbo loans price off different funding, FHA and VA loans carry government guarantees, and the 15-year rate sits below the 30-year because the lender's money is out for half as long.
Sources: Optimal Blue Mortgage Market Indices (OBMMI), via FRED; Freddie Mac Primary Mortgage Market Survey®, via FRED (copyright Freddie Mac, reprinted with permission). Both are shown under their owners' terms and are not offered as downloads here.
Enter your price, down payment and term and the calculator prints the monthly payment at today's lock rate (prefilled from the daily index, editable): principal and interest, plus your own property tax, insurance, HOA and mortgage insurance if you add them, with the loan amount, the total interest over the term, how the first payment splits between interest and principal, the month principal overtakes interest, and what a quarter or half point either way does to the payment.
Pick a state and the calculator fills the property tax and the homeowners insurance it would carry: the effective property tax rate is median real estate taxes paid against median home value from the Census American Community Survey five-year estimates, applied to the price entered, and the insurance figure is the average premium per policy across that state's ZIP codes from the Treasury Federal Insurance Office homeowners data. Both are state averages, both carry their vintage on the page, and both can be typed over with your own quote.