A weekend figure such as four tenths of a percent means little as a bare number. It could be a large move or a shrug. The options market has already published a yardstick for it. The expected move says how far the market is priced to travel, and a weekend move reads far better as a share of that range.
The yardstick
The expected move is the range implied by option prices for a given expiry. It is taken from what traders paid for the at-the-money options, so it is the market’s own pricing of how far the index might go. The expected move has the full definition. On 2 October 2026 SPY’s expected daily move was 0.46%.
Reading the move as a fraction
Divide the perp’s move since the cash close by the expected move. Well under half, and the weekend has done little by the options market’s own measure. Close to one, and the perp has already traveled a full day’s priced range before the bell. Well over one, and the perp is showing something Friday’s option prices had not allowed for.
The fraction also makes weekends comparable. The same percentage move is a bigger event when the expected move is small than when it is large. A bare percentage hides that. A fraction shows it.
Which expected move to use
Be clear about the period. A daily expected move describes one session. A weekend spans more calendar time, and news does not stop for it. The options that expire on Monday were priced on Friday with the weekend inside them. Their expected move is the closer comparison for a weekend move. The daily figure still works as a common unit, as long as you say which one you used.
What it changes at the open
For a 0DTE trader the fraction is a warning about Friday’s levels. The expected-move boundaries on Friday’s map were drawn around Friday’s close. If the perp has already used most of that range, Monday’s contracts reprice from a new center. Strikes that sat out of the money on Friday afternoon may be at the money at the bell. The expected move against the gamma walls shows how the two sets of levels interact once the session is live.
Where it breaks
The perp’s move is a market price on another venue, formed in thinner depth than a weekday. The expected move is a priced range and never a limit. Neither says where the cash market opens. The fraction tells you how large the weekend looks against what was priced, and that is all it tells you.
Trader shows the expected move for SPY, QQQ and IWM beside the index perps’ move since the close. Its weekend push is sized at half a percent, which is about one expected daily move for SPY on that October reading. The half-percent alert explains the choice.