What is the expected move? How is it calculated?

Ask a 0DTE trader how far SPX is likely to move today and you'll usually get a guess.

The market already answered that question. It answers it every minute, in real money.

The answer is called the expected move. It's the options market's own estimate of how far a stock or index is likely to travel between now and expiration. It's written as a plus-or-minus number, like ±24 points.

If you bet on sports, you already understand it. The expected move is the closest thing options have to a point spread. Nobody decides it in a back room. It comes from where people are putting their money.

You wouldn't bet a game without knowing the spread. Don't trade the day without knowing the move.

If you're new here, two earlier posts set this one up: What is a put option? What is a call option? and What is 0DTE?

How it's calculated: add two prices

The simplest method takes thirty seconds and no math degree.

1. Find the strike closest to the current price. That's the at-the-money strike.
2. Look up the price of the call at that strike.
3. Look up the price of the put at that strike.
4. Add them together.

That's the expected move. Traders call the pair an at-the-money straddle. If the words call and put are still new, the put and call post covers both.

Here's a real one. On October 6, 2026 at 10:00 AM Eastern, SPX was at 7826.29. The closest strike was 7825. These were the 0DTE quotes:

$12.15 plus $11.55 is $23.70. The expected move was ±23.70 points. That put the day's expected range at roughly 7803 to 7850.

Why does this work? Think about who owns that straddle. They paid $23.70 for a call and a put together. They only profit if SPX finishes more than 23.70 points away from 7825, in either direction. The seller only profits if it doesn't.

Buyers and sellers argue over that price all day. Where they settle is the market's best guess at the size of the move.

Why your broker's number might not match

There's more than one way to calculate an expected move. Three are common.

1. The straddle. Call plus put at the money. That's the method above.
2. A blended version. Some platforms take a fraction of the straddle, often 85%. Others blend the straddle with the next strikes out on each side. These give a slightly smaller number.
3. The volatility formula. This one starts from implied volatility.

Expected move = price × implied volatility × the square root of (days to expiration ÷ 365)

Say an index is at 7,800 with 16% implied volatility and one day left. That's 7,800 × 0.16 × 0.0523, or about 65 points.

The formula gives what statisticians call a one standard deviation move. The straddle usually comes out near 80% of that number.

None of these is wrong. They're different rulers. What matters is that you know which one your platform uses and that you don't mix them.

I prefer the straddle for 0DTE. It needs no model and no assumptions. It's a price you could trade right now.

What it tells you, and what it doesn't

The expected move is the most useful number in 0DTE. It's also the most misread. Four things to get straight.

It's a typical move, not a ceiling. This is the big one. Traders treat the expected move like a wall. It isn't.

Go back to that October 6 board. The 7850 call sat almost exactly one expected move above spot. Across 1,101 past sessions, calls at that distance at 10:00 AM:

• Went in the money at some point during the day 38.1% of the time.
• Finished the day in the money 21.5% of the time.

Puts one expected move below spot finished in the money about as often. Put the two sides together and the day ended outside the expected move roughly four times in ten.

That's not a wall. That's a coin with a slight lean.

It says nothing about direction. The expected move is plus or minus. The market is telling you how far, not which way.

It shrinks all day. Less time left means less room to move. The 10:00 AM number is not the 2:00 PM number. A strike that was far away this morning can be close this afternoon without the index moving at all.

It's an estimate, not a promise. Some days the market travels half the expected move. Some days it travels three times as far. The estimate is honest. It's just not a guarantee.

Why it's the ruler for every strike

Here's a question I hear constantly. Is a strike 25 points away from spot near or far?

You can't answer that in points.

On a quiet day with an expected move of ±15, a strike 25 points out is a long way off. On a wild day with an expected move of ±60, that same strike is next door. Same 25 points. Completely different trade.

So stop measuring in points. Measure in expected moves.

• 25 points out on the quiet day is about 1.7 expected moves.
• 25 points out on the wild day is about 0.4 expected moves.

Now the two days can be compared. A strike one expected move away on a Tuesday in March is the same kind of trade as a strike one expected move away on a Friday in October. That's true even though the point distances are nothing alike.

This matters whether you buy or sell. Buyers want to know how far out is too far to ever pay. Sellers want to know how close is too close to be safe. Both questions are about distance, and distance only means something against the expected move.

Know the move before you pick the strike

The expected move is one number. You can calculate it yourself in thirty seconds. Call plus put at the money.

It won't tell you which way the market goes. It will tell you how big a day the market is pricing in, and it turns every strike on the board into a distance you can compare with history.

That's exactly how StrikeZone IQ uses it. Every figure on the site is measured against the expected move. Then it counts how often strikes at that same distance, at that same minute, actually paid off or went in the money in real past sessions.

Those are historical odds, not predictions. But I'd rather decide with the record in front of me than without it. The 9:45 AM ET board is free.

Next up: how often does SPX really close outside its expected move? I'll count every session since May 2022.