How Interest Rates Actually Work: From the Fed to Your Mortgage
When the Fed cuts interest rates, the story goes, borrowing gets cheaper across the board — your mortgage, your car loan, your credit card, all of it. It’s clean, intuitive, and wrong often enough to cost you money. The Fed sets exactly one interest rate, and it isn’t the one on your mortgage, your card, or your savings account. What happens to those is a chain, not a switch — and some links in that chain are loose, slow, and occasionally run backwards.
The one rate the Fed actually controls
There’s no dial in Washington labeled “mortgage rates.” The Fed controls the federal funds rate — and even that it doesn’t set directly. It sets a target range and steers the effective rate into it using its other tools.
The federal funds rate is the interest banks charge each other to borrow overnight. Banks have to hold a certain amount in reserve; at the end of the day some are short and some have extra, so they lend to each other overnight to settle up. The rate on that bank-to-bank overnight loan is the federal funds rate. It’s the number at the center of every Fed headline, and it is not a rate you or I will ever pay directly. We live downstream of it.
The tight links, where a cut shows up fast
From that one overnight rate, everything else reprices — but at wildly different speeds. The tightest link is the prime rate, what banks charge their most creditworthy borrowers. Prime isn’t really negotiated; by convention it’s the federal funds rate plus about three percentage points, and it moves the same day the Fed does, in lockstep.
A whole category of consumer debt is pinned directly to prime: most credit cards, home equity lines of credit, and plenty of variable-rate personal loans. So when the Fed cuts, the interest on your credit card balance really does ease within a statement cycle or two — it’s bolted to prime, which is bolted to the Fed. This is the part of the simple story that’s actually true. If every rate worked like a credit card, the simple version would be right.
The loose link, why your mortgage ignores the Fed
The biggest loan most people ever take doesn’t work that way. A thirty-year mortgage doesn’t track the federal funds rate. It tracks the ten-year Treasury yield — and the ten-year moves on something completely different: expectations.
The federal funds rate is an overnight rate; it’s about right now. A thirty-year mortgage is money lent for decades, so its rate reflects what investors think inflation and growth will do over years, not what the Fed did this afternoon. Which leads to the part that breaks people’s intuition. A Fed cut can leave your mortgage rate exactly where it was, because the market saw the cut coming and priced it in weeks ago. Or, stranger still, a cut can push mortgage rates up: if investors decide the Fed is easing too aggressively and will let inflation run hot, they demand higher yields on long-term bonds to compensate — and mortgage rates climb on the very day the Fed eased. It has happened before, and it will happen again.
Your savings, and the asymmetry
Flip it around to the money coming in. The yield on your savings account, your money market, and your certificates of deposit tracks the federal funds rate too, because when money is expensive between banks, banks compete harder for your deposits. Higher fed funds rate, better savings yield.
But the pass-through is asymmetric, and that’s the catch worth knowing. When the Fed hikes, banks are slow to raise what they pay you on savings — they’re in no rush to give up the spread. When the Fed cuts, they’re quick to lower it. The chain runs both directions, but the direction that benefits the bank tends to move faster. Knowing that is the difference between leaving money on the table and moving it.
A chain, not a switch
So when a headline says the Fed moved, picture what actually happens. The Fed pushes on one end of the system — a single overnight rate between banks. From there it travels outward through a web of linkages. Some are tight and fast, like your credit card. Some are loose and stubborn and occasionally backwards, like your mortgage. The Fed doesn’t flip a switch on your financial life; it pushes one rate, and the rest of the structure responds at its own speed, in its own direction.
Which means the question on a Fed day was never “did my rate just change.” It’s which of your rates is tied to this one, how tightly, and what the market already expected. Answer that, and a Fed decision stops being a headline you react to and starts being something you can actually read.
Not investment advice. WTH Markets is editorial commentary, not financial guidance.
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