Article

Why a single gamma number misleads you

You check a gamma chart at 2pm. There is a wall at 605 — a large positive concentration, exactly where price has been stalling all afternoon. You build a trade around it. Next morning the wall is gone, price sails through 605 without pausing, and nothing about your reasoning was wrong except one thing you were never shown.

Gamma is not evenly spread through time

An option's gamma is highest when it is closest to expiry and closest to the money. That is not a quirk; it is the definition. Gamma measures how fast delta changes, and delta has to travel the entire distance from 0 to 1 by expiry. The less time remaining, the more violently it moves.

A contract expiring in thirty days drifts. A contract expiring in three hours snaps. So when you aggregate gamma across every expiry into one headline number, contracts that will not exist tomorrow dominate a figure you are reading as structure.

How same-day gamma behaves through a session

0DTE gamma intensifies as expiry approaches — hedging gets more forceful through the afternoon — and then goes to zero at the close. The level it was defending stops existing.

Two walls that look identical

On a blended chart, these are indistinguishable. One is built from open interest accumulated over weeks by participants with multi-week horizons. The other is built almost entirely from options bought this morning that expire this afternoon.

Same wall, two different sources

Where the 0DTE-only bars account for most of the height, the wall is an intraday artefact. Where they account for little, longer-dated positioning is holding the level and it will still be there tomorrow.

The first will still be there tomorrow. The second evaporates at 16:00, and any trade premised on it surviving the night was premised on nothing.

The test takes five seconds

Look at the level with all expiries included, then look at it with only today's expiry selected. Compare.

Present in both — durable. Real multi-week positioning is behind it. Tradeable as structure, and likely to matter tomorrow.
Only in the 0DTE view — intraday only. Genuinely powerful today, especially into the close, and completely gone by the next open.
Only when 0DTE is excluded — a longer-dated level that today's flow is currently overwhelming. Worth noting for later in the week.

None of these is the "right" answer. A 0DTE wall is real and often the dominant force in an afternoon session — it is simply the wrong thing to hold overnight. The mistake is not trading it; the mistake is not knowing which kind you are looking at.

Why this matters more each year

Same-day options have grown from a niche product into a substantial share of index options volume. That growth means the share of total gamma that expires today has risen with it — so the gap between "gamma right now" and "gamma that persists" has widened, and the blended reading has become correspondingly less useful.

Any tool that shows you one gamma number without letting you separate expiries is showing you a blend of two different things. FlowRadar's expiry picker exists for this reason: selecting a single expiration recomputes the levels for that expiration alone, so you can see exactly which part of the structure survives the close.

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