The expected move is the range that option prices imply for the session. It is quoted once and most traders read it once, before the bell. By early afternoon the number on the screen means something different, because part of the day is over.
Two subtractions
The first is range. Price has traveled some distance from where it started, in one direction or both. Set against the expected move, that distance shows how much of the implied range the day has already delivered.
The second is time. A session has a fixed length and some of it is gone. The two subtractions are separate. A day can use most of its range in the first hour, or almost none of it by lunch.
Range does not shrink in step with time
It is tempting to say that half a day left means half a move left. The standard assumption in option pricing is that range grows with the square root of time. Under it, half a session still carries about seven tenths of a full session’s implied range. The remaining range falls more slowly than the clock, until late in the day when it falls quickly.
That is a model, and the session is uneven. The open and the close are busier than the middle. Treat the square-root rule as a correction to the half-and-half instinct. It is too rough to be used as a measurement.
What the comparison shows
Price at the edge of the expected move with most of the session ahead is one situation. The day has already delivered what options priced, and there is a lot of time for it to deliver more or to give some back. Price at the same edge with an hour left is another. Little time remains for either.
Neither reading predicts the next move. Each one is context for a setup such as the expected-move boundary trade, where the same level deserves a different weight at different hours.
The option’s side of it
An out-of-the-money same-day option is priced almost entirely on time. Its time value drains faster as the close approaches, which is the subject of why same-day theta accelerates. So the question to put to any strike in the afternoon is whether the distance to it fits inside what the remaining time implies. Judging a strike against the expected move is the same test, run with the clock included.
Where NoVo shows it
Trader shows the expected move on SPY, QQQ and IWM beside the gamma flip and the walls, on a 5-minute cycle on Trader Pro and live on Trader Max. The time left is on the clock. The comparison is the trader’s to make.