How much does a rate change cost you?

Roughly 10% of the price, though it depends on your down payment and how much of the payment goes to taxes and insurance rather than the loan. Enter your own numbers above — the table holds your payment steady and shows the price each rate reaches, which is the comparison that actually matters when you are shopping.

Nobody can tell you reliably where rates go next, and waiting has costs of its own: prices, competition and your rent all keep moving. What this calculator shows is the size of the trade-off, so the decision is yours with the numbers in front of you rather than a guess about the bond market. If rates do fall later, refinancing is available; if prices rise while you wait, that is not recoverable.

They solve different problems. Extra down payment reduces the loan and can remove mortgage insurance; buying the rate down lowers the interest for as long as you keep the loan, and a temporary buydown is often funded by the seller rather than you. The right answer depends on how long you will keep the loan and where your cash is more useful — worth a conversation rather than a rule of thumb.

Because taxes, insurance and mortgage insurance do not fall when rates rise. They are a fixed share of the payment, so the entire rate increase comes out of the part that services the loan. That is also why St. Louis buying power reacts differently than a national calculator suggests — local tax and insurance costs are part of the math.