What is gamma exposure (GEX)?

Somebody sold you that option, and to survive it they have to keep buying and selling the underlying stock all day. Gamma exposure is an attempt to add up how much stock, across every contract on the board. It explains a real mechanism — and it rests on one assumption you should know about before you trust the number.

Start with one option and one hedge

A market maker sells you a call on a $100 stock. They do not want a bet on direction; they want the spread. So they buy stock to offset the call they are now short. How much stock? That is delta — the number of shares the option currently behaves like. An at-the-money call has a delta near 0.50, so one contract (100 shares) needs about 50 shares of hedge.

Here is the problem: delta does not stay put. If the stock rallies, the call starts behaving more like stock and its delta climbs toward 1.00. Now the dealer's 50 shares are not enough and they must buy more. If the stock falls, delta drops and they must sell. The rate at which delta changes as price moves is gamma, and it is the reason hedging is a continuous activity rather than a one-off trade.

The direction of the flow is the whole point

Whether that hedging calms the market or feeds it depends on which side of the gamma the dealer is on.

• Dealer long gamma (positive). Price rises, their delta rises above the hedge, so they sell stock. Price falls, they buy. The flow leans against whatever just happened.
• Dealer short gamma (negative). Every rally forces them to buy and every dip forces them to sell, in the same direction the market is already going. The flow leans with whatever just happened.

That is the mechanism the whole GEX industry is built on, and the mechanism itself is not controversial: hedging flows are real, they are large, and they are forced.

The arithmetic, written out

Take a $100 stock and one call struck at $100, thirty days out, with implied volatility of 25%. A standard option-pricing model puts that contract's gamma at about 0.0556. Suppose 10,000 of them are outstanding.

gamma per share                     = 0.0556
contracts outstanding               = 10,000
shares per contract                 = 100

delta change per $1 move
  = 0.0556 x 10,000 x 100           = 55,600 shares

the stock is $100, so a 1% move is $1

dollar gamma per 1% move
  = 55,600 shares x $100            = $5.56 million

So a single 1% move obliges the dealers holding that one strike to trade roughly $5.6 million of stock just to stand still. Do that for every strike and every expiration, count calls as positive and puts as negative, and you get the market-wide figure quoted as net GEX per 1% move. The general form is:

GEX = sum over all contracts of
        gamma x open interest x 100 x spot^2 x 0.01
      with calls positive and puts negative

Net, gross, flip and walls

Four numbers appear on every GEX page here, and they answer different questions.

• Net GEX is calls minus puts. Its sign is the headline: positive means the damping regime, negative the amplifying one.
• Gross gamma adds everything up ignoring sign. It measures how much hedging is going on in total. A small net inside a huge gross means the two sides nearly cancel — and that a modest shift in positioning could flip the sign.
• The gamma flip is the price where net gamma would cross zero. Distance to the flip is the useful part: sitting on top of it means the regime is unstable and could change on any ordinary session.
• Gamma walls are the individual strikes holding the most gamma. Hedging intensifies near them, but they are concentration markers, not barriers — we have not measured whether price respects them.

The assumption you have to know about

Every free GEX number, including ours, assumes that dealers are long every call and short every put. That is a convention, not a measurement. Open interest tells you how many contracts exist; it does not tell you who is holding which side. If a large customer happens to be short calls and long puts on a name, the true dealer position is the opposite of what the convention assumes, and the sign of the estimate is simply wrong for that ticker.

Stacked on top of that:

• End-of-day inputs. Open interest settles overnight. GEX cannot update intraday, whatever a live-looking dashboard implies.
• A simplified pricing model. We use Black-Scholes with a zero interest rate and no dividends, which is the common public convention. It is close enough for shape, not for precision.
• Real books are not one product. A market maker hedges an equity option book with futures, other expirations, ETFs and correlated names. None of that is visible in a single ticker's open interest.
• The number is not the mechanism. Hedging flows are real; the aggregate estimate of them is fuzzy. Trust the sign and the rough magnitude, not the decimal places.

How to use it without fooling yourself

• Set expectations, not entries. A negative-gamma reading describes estimated hedging flow that leans with price rather than against it. That is the mechanism, not a measured outcome, and it is not a reason to be short.
• Watch the distance to the flip, not just the sign. The flip level is recomputed every night from new open interest, so a regime sitting close to it can invert on an ordinary session. How long a regime lasts at a given distance is not something we have measured.
• Check the expiration table. Gamma is not spread evenly across expirations, and the split differs by ticker. In the nightly files behind the table below, the expiration nearest each file's own snapshot date accounted for a median of 9.3% of that ticker's gross gamma, and for more than half of it in only 0 of 43 tickers. That denominator covers only the expirations stored in those files, none of them more than 50 days past the snapshot date the file carries. Read the breakdown instead of assuming the front expiration dominates, because a large expiry can reset the whole picture.
• Cross-check it. When gamma positioning and max pain point at different levels, that disagreement is more informative than either number alone — max pain vs gamma exposure works through the four configurations you will actually see.

The latest gamma exposure levels

Every ticker with a chain deep enough to estimate gamma — 43 of them, 26 currently reading positive. Computed nightly from end-of-day open interest and closing quotes. Latest snapshot in this table: 2026-09-03.

All tickers, including those without a GEX estimate

Common questions

What is GEX in options trading?

GEX, short for gamma exposure, estimates how much stock the dealers who sold options must buy or sell to stay hedged when the underlying moves 1%. It is calculated by summing gamma times open interest across every listed contract, with calls counted positive and puts negative, then converting to dollars. A positive total suggests hedging flows lean against the market and damp moves; a negative total suggests they lean with it and amplify moves.

What does the gamma flip level mean?

The gamma flip is the price at which the aggregate gamma estimate crosses zero. Above it the market is estimated to be in a positive gamma regime, where dealer hedging sells rallies and buys dips. Below it the regime is negative and hedging does the opposite. Because it is derived from the same open interest, the flip level moves every night and can be crossed by an ordinary session when it sits close to the current price.

What is the difference between gamma and delta?

Delta is how many shares an option currently behaves like — a call with 0.50 delta moves roughly 50 cents when the stock moves a dollar. Gamma is how fast that delta changes as price moves. Delta tells a dealer how much stock to hold right now; gamma tells them how much that requirement will change if the price moves, which is what forces them to keep trading.

What does a positive versus a negative gamma regime describe?

Neither is good or bad — they describe different environments. In a positive gamma regime the estimated hedging flow leans against price: dealers sell into rallies and buy dips. In a negative one the same flow leans with price, pushing moves further in the direction they were already going. That is a description of the mechanism, not a measured hit rate — we have published no measurement of what ranges actually do in either regime. Which regime the estimate suggests is context for what to expect, not a reason to take a position.

How accurate is public GEX data?

It is an estimate with known weaknesses. Public GEX assumes dealers are long every call and short every put, which is a convention rather than a measurement; open interest does not reveal who is on which side. It also uses end-of-day data, a simplified option-pricing model, and ignores that real market makers hedge across futures, other expirations and other products. Treat the sign and the rough magnitude as informative and the precise number as noise.

Read next

What is max pain? works through the other calculation built on the same open interest — the expiry-payout balance point — by hand. Max pain vs gamma exposure compares the two directly and shows what a disagreement between them is actually telling you.

Gamma exposure here is a derived estimate computed nightly from end-of-day open interest and closing quotes using a Black-Scholes approximation with zero rate and zero dividend (how we compute it). Not raw market data, not a live quote. Educational only: not investment advice, not a recommendation, not a price forecast.