"Markets are pricing a 70% chance the Fed hikes next month." You have seen that sentence a hundred times. It is not a poll, and no one asked any traders what they think. The number is extracted, mechanically, from the prices of a specific futures contract. Once you see the arithmetic, rate-odds charts stop being a black box — and you also learn exactly when not to trust them.
The instrument: 30-Day Fed Funds futures
The federal funds rate is the interest rate U.S. banks charge each other for overnight loans of reserves. The Fed steers this rate into a target range — say 3.50–3.75% — and the actual daily traded value inside the range is published as EFFR, the Effective Federal Funds Rate.
CME lists a futures contract on this rate: 30-Day Fed Funds futures. Each monthly contract settles at 100 minus the average daily EFFR for that calendar month. If the average EFFR over November turns out to be 3.63%, the November contract settles at 96.37. So the price of the contract is a market forecast of the average funds rate for its month — buy it too cheap or sell it too rich and you lose real money, which is what keeps the forecast honest.
From a price to a probability
Here is the core logic in three steps, with real numbers.
- Step 1 — read the implied rate. Suppose the futures contract for next month trades at 96.30. Implied average EFFR: 100 − 96.30 = 3.70%.
- Step 2 — line up the two possible worlds. Say the current EFFR is 3.63% and there is one FOMC meeting mid-month. If the Fed holds, the month's average will be about 3.63%. If it hikes by 25 basis points, days after the meeting will run near 3.88%, making the month's average land somewhere between — the exact value depends on which day of the month the meeting falls.
- Step 3 — solve for the mix. The futures-implied 3.70% sits between the "hold" world (3.63%) and the "hike" world (say 3.73% average, if the meeting is mid-month). The market is pricing a weighted blend: 3.70 = p × 3.73 + (1 − p) × 3.63. Solving gives p ≈ 0.7 — a 70% implied probability of a hike.
That is the entire trick, and it is the same method CME's well-known FedWatch tool uses: assume the funds rate only jumps on meeting days, read the month-average from the futures price, and back out the probability mix that explains it. For meetings further out, the calculation chains forward month by month, which is why far-dated odds are fuzzier — each step inherits the assumptions of the previous one.
Reading an odds chart properly
A rate-odds display shows a probability for each possible target range at an upcoming meeting — for example: 0% chance of a cut, 31% no change, 69% hike. Three habits make the reading honest:
- Watch the change, not the level. Odds moving from 40% to 70% hike over a week is the story — it means incoming data or Fed communication repriced expectations. A static 70% is just the current consensus.
- Expect violence around data releases. A hot CPI print can move next-meeting odds 20 points in minutes, because the futures reprice instantly. The odds are a live derivative of market prices, not a slow-moving poll.
- Distrust precision far out. Odds for a meeting three or four months away routinely swing from "certain cut" to "certain hold" and back. The market is not clairvoyant; it is aggregating today's information, which decays fast.
What the odds are not
Implied probabilities are risk-neutral — they blend true expectations with hedging demand and risk premium. When markets are stressed, buying Fed funds futures is partly insurance, which distorts the implied odds away from pure forecasts. The practical version of this caveat: treat 55% vs 45% as "roughly a coin flip, leaning hike," not as a precise statement. The odds are the best rate forecast available anywhere, and they are still just a forecast.
One more distinction worth keeping straight: the target range is what the Fed announces (3.50–3.75%); EFFR is what actually prints in the market each day (3.63%). The futures settle on EFFR, so all implied odds are really statements about where EFFR will average — the market's bet on what the Fed does, expressed through the rate it controls.
Finza's Fed Rate Monitor computes these probabilities live from 30-Day Fed Funds futures using the meeting-date methodology described here, alongside the FOMC countdown and a summary of recent Fed commentary — so the number, its inputs, and its context sit on one screen.