How the gamma exposure formula gets its units
Enter gamma as the change in an option's per-share delta for a $1 move in the underlying. For each row, multiply gamma by open interest and the contract multiplier to obtain the change in delta-equivalent units per $1. A 1% move is 0.01 × spot; valuing those units at the starting spot gives:
GEX / +1% = sign × gamma × OI × multiplier × spot² × 0.01
The sign is +1 for an assumed long position and -1 for an assumed short position. Both long calls and long puts have positive gamma, as explained in OIC's gamma reference. A negative put contribution is a position assumption, not a property of put gamma.
This is a local approximation of the gamma-driven change in dollar delta-equivalent exposure. It is neither option profit and loss nor premium notional. A per-$1 GEX convention instead uses gamma × OI × multiplier × spot. To compare that convention with this page, multiply it by 0.01 × spot.
Reproduce the $100 spot example
Click Load example to restore two hypothetical contracts at the $100 strike. Each has a multiplier of 100. The call has gamma 0.02 and OI 1,000; the put has gamma 0.03 and OI 800.
| Row | Unsigned calculation | Exposure / +1% |
|---|---|---|
| Call | 0.02 × 1,000 × 100 × 100² × 0.01 | $200,000 |
| Put | 0.03 × 800 × 100 × 100² × 0.01 | $240,000 |
Long calls and short puts produce -$40,000. Reversing both positions produces +$40,000. Assuming both are long gives +$440,000; assuming both are short gives -$440,000. The chain data has not changed. Only the position assumption changed.
At a hypothetical spot of $200 with the same gamma inputs, every magnitude would be four times larger because of the spot-squared term. Actual option gamma would also change as spot moves, so that exercise tests the formula rather than repricing the contracts.
Check chain inputs before interpreting the sign
- In TradingView, match the underlying, strike, call/put type and expiration. Its options chain overview documents contract Greeks. An individual contract's gamma is not aggregate market GEX.
- Obtain open interest for the same contracts from a source that supplies it. Record the OI date separately from the quote and gamma timestamp. Volume counts trades and cannot substitute for open interest. If a field is absent, leave it missing until you can verify it.
- Confirm gamma units and the contract multiplier. Use only contracts whose delta units and USD underlying price are compatible. Adjusted deliverables, futures options, and mixed currencies need their own unit treatment; changing a multiplier alone may be insufficient.
- Enter each contract once. Multiple expiries at the same strike are summed, so keep a record of which expiries and strike range you included. The result describes the entered sample, not necessarily the full chain.
- Compare all four position assumptions before interpreting a signed total. None of these scenarios estimates the probability that dealers actually hold those positions.
Why open interest cannot establish dealer gamma
Each outstanding contract has a long and a short side. OI does not allocate those sides to dealers, customers or other participants. Assigning all calls one sign and all puts another models a hypothetical subset of positions. It does not measure the net gamma of every participant combined.
Cboe's analysis of SPX 0DTE hedging explains why the balance of buying and selling matters for market-maker exposure. Under delta hedging, a long-gamma book tends to sell underlying after a rise and buy after a fall; a short-gamma book does the reverse. Those conditional mechanics do not tell this calculator who holds the book or how much they will trade.
Limits of this strike chart
A sign change between two strike bars does not locate the underlying price where total gamma flips. A gamma-flip calculation must reprice all included contracts at a range of underlying prices, with expiry, volatility and model assumptions, then search for a zero in the total. This calculator holds the supplied gamma values fixed and therefore does not report a zero-gamma price.
Missing expiries, stale OI, changing volatility, new intraday trades and offsetting positions can change the estimate. A large bar is a concentration in the selected scenario, not proof of support, resistance, pinning or a coming squeeze. Zero net GEX can also hide large offsetting call and put contributions.
Use the option Greeks calculator to study individual-contract sensitivity, or compare the different expiration-payoff question in the max pain calculator. More workflows are in the TradingView workflows hub.
This calculator is for education and scenario analysis, not investment advice. Options involve risk.