How the Fed Actually Moves Your Interest Rates: The Mechanism, Start to Finish

Eight times a year, a committee meets in Washington, releases a few paragraphs at 2 p.m. Eastern, and within minutes headlines announce that "the Fed raised rates" or "the Fed cut rates." What almost never gets explained is the plumbing: which rate, exactly? Set how? And by what chain does a number for overnight loans between banks end up changing what you pay on a credit card in Tucson or a mortgage in Toledo?

This is a systems walkthrough. No forecasts, no opinions about whether policy is too tight or too loose — just the machine, start to finish.

Step one: what the Fed actually decides

The Federal Open Market Committee (FOMC) — seven governors plus a rotating cast of regional Reserve Bank presidents, twelve voters in all — sets a target range for the federal funds rate: the interest rate banks charge each other for overnight, unsecured loans of the deposits they hold at the Fed. The range is a quarter of a percentage point wide, which is why you hear things like "a target range of X to X-and-a-quarter percent."

Step two: how the target becomes reality

Here's the part that changed after 2008 and that most explainers still get wrong. In the old days, the Fed kept bank reserves deliberately scarce and nudged the funds rate by buying and selling small amounts of Treasury securities daily. That machinery is gone. Since the financial crisis — and formally, in the Fed's own framing, since 2019 — the Fed operates an "ample reserves" regime, described in detail in the St. Louis Fed's teaching materials and the Board's implementation notes. Banks hold abundant reserves, and the Fed steers the market rate using two administered rates it simply sets by announcement:

Interest on reserve balances (IORB). The Fed pays banks interest on the money they park in their Fed accounts. No bank will lend overnight to another bank for less than it can earn risk-free from the Fed itself, so IORB acts as a magnet just below the top of the target range.

The overnight reverse repo rate (ON RRP). Money-market funds and other non-banks can't earn IORB, so the Fed offers them a parallel deal: park cash at the Fed overnight against Treasury collateral, at a posted rate. That sets a hard floor under short-term rates for the players outside the banking system.

Raise both administered rates a quarter point, and the entire overnight money market shifts up a quarter point within a day — no securities need to be bought or sold. That's the whole trick. (The Fed also keeps a ceiling: the discount window and a standing repo facility lend to banks at the top of the range, capping spikes.)

The transmission chain: one vote, many rates

How an FOMC decision propagates to the rates you actually pay

Step three: the fast channel — prime-linked rates

Now the decision leaves the Fed's building. The fastest transmission runs through the prime rate, the benchmark banks use for many consumer and small-business products. By longstanding convention, U.S. banks set prime at the top of the fed funds target range plus 3 percentage points, and they reprice it within a day or two of an FOMC move.

Deposits ride the same channel — with friction. Banks raise savings rates only as fast as competition forces them to, which is why in every hiking cycle the gap between the funds rate and the average savings-account rate widens before high-yield accounts and money-market funds (which pass through the ON RRP floor much more directly) drag it closed.

The upshot: the FOMC influences mortgage rates the way a lighthouse influences ships — through signals, guidance, and credibility, not a rope.

Step four: the slow channel — the bond market and your mortgage

The 30-year fixed mortgage — the rate Americans care most about — does not follow the fed funds rate mechanically. It follows the 10-year Treasury yield, plus a spread. And the 10-year yield is a market price reflecting what thousands of investors expect short-term rates to average over the next decade, plus compensation for inflation risk and an extra "term premium" for locking money up.

That single fact explains most mortgage-rate behavior that otherwise looks perverse:

• Mortgage rates move before the Fed does. If markets become convinced cuts are coming, the 10-year yield falls on the expectation, and mortgage rates ease ahead of any actual FOMC action. The reverse happened in 2022, when mortgage rates roughly doubled while the Fed was still early in its hiking cycle — markets had priced the whole campaign.
• A Fed cut can coincide with rising mortgage rates, if the market simultaneously revises up its longer-run expectations for inflation or borrowing (which is one place fiscal policy and federal debt dynamics leak into your housing costs).
• Why a spread at all? Mortgages get bundled into mortgage-backed securities, and investors demand extra yield for prepayment risk — your right to refinance whenever rates drop. That spread historically runs in the neighborhood of one and a half to two-plus percentage points over the 10-year, widening when markets are stressed.

The upshot: the FOMC influences mortgage rates the way a lighthouse influences ships — through signals, guidance, and credibility, not a rope. Its statements, projections, and press conferences are engineered precisely because the expectations channel is where long-term rates are made.

The other dial: the balance sheet

Why the Fed is doing any of this

The machine exists to serve the Fed's congressional mandate: maximum employment and stable prices (it targets 2% inflation over time — the reasoning behind that number, and why the goal is slower price increases rather than price declines, is central to why grocery prices don't come back down). Raising rates makes borrowing dearer and saving more rewarding, cooling spending, hiring, and price pressure; cutting does the opposite. Whether any particular stance is right is permanently contested territory among economists and politicians — this explainer takes no side. The mechanism, though, isn't contested; it's published, in unusual detail, by the Fed itself.

Watching it work: a recent tour of the dial

The target range's recent history shows the machine's dynamic range. It sat near zero after the 2008 crisis, rose gradually to 2.5% by 2019, was slammed back to near zero in March 2020, then climbed at the fastest pace in four decades — eleven hikes across 2022 and 2023 — to a peak of 5.5% (upper bound), before cuts began in late 2024, bringing it to 4.5% by that year's end.

One dial, four decades of range

Federal funds target (upper bound), year-end, selected years — %

Each of those moves ran the same relay: a vote on a range → two administered rates reset → overnight markets shift by the next morning → prime reprices within days → card APRs and HELOCs follow within weeks → deposit rates grind along behind → and, all the while, the bond market translates the expected path of future votes into the 10-year yield, which sets what a lender quotes on a ranch house in Ohio. (That quote, multiplied across every buyer and builder in the country, is one of the levers pressing on America's housing shortage.)

That's the whole machine. No vault of money being opened, no single "interest rate" lever — just a committee, two posted numbers, a convention called prime, and a bond market doing the long-distance transmission. The next time the 2 p.m. statement drops, you'll know exactly which gears start turning, in which order, and which of your own numbers will move — and which will wait on what the market believes comes next.

Primary Sources

1. Federal Reserve Board, Interest on Reserve Balances (IORB) FAQs
2. Federal Reserve Board, Open Market Operations & policy implementation
3. Federal Reserve Bank of St. Louis, "The Fed's Balance Sheet and Ample Reserves" (Page One Economics, 2026)
4. Federal Reserve Bank of New York, Effective Federal Funds Rate data
5. Federal Reserve Board, Federal Open Market Committee — meeting calendars and statements