Strike price (options)
A strike is the price at which an option contract can be exercised: a call gives the right to buy the underlying at the strike, a put the right to sell it there. Strikes are the axis along which gamma exposure, open interest and options flow are usually organised.
Senzoukria · Glossary · Updated September 2026
What a strike defines
Every listed option carries four identifiers: underlying, expiry, type (call or put) and strike. The strike fixes the exercise price. A call with a 5,000 strike gives its holder the right to buy the underlying at 5,000; a put with the same strike gives the right to sell there. Whether that right has value depends on where the underlying trades relative to the strike, which is what the terms in-the-money, at-the-money and out-of-the-money describe.
Exchanges list strikes on a grid whose spacing depends on the underlying's price and the expiry. Near-dated index options usually carry a denser grid than long-dated ones, and new strikes are added when the underlying moves outside the existing range. A chain therefore does not have the same strike coverage from one day to the next.
Why strikes matter for gamma exposure
- Gamma is concentrated near the strike: an option's gamma peaks when the underlying is at the strike and decays as it moves away, faster for short-dated contracts.
- Open interest is reported per strike, so any GEX estimate is a sum over strikes weighted by gamma, open interest and the contract multiplier.
- A call wall or put wall is the strike that ranks first under a chosen metric (largest open interest, largest gamma-weighted exposure, or largest signed exposure). Different metrics can pick different strikes for the same chain, as the guide on gamma walls shows.
- The gamma flip is not a strike; it is a price where the modeled net exposure changes sign, usually found between strikes by interpolation.
From an index strike to a futures level
A SPY or SPX strike is not an ES price, and a QQQ or NDX strike is not an NQ price. The ETF, the index and the futures contract trade on different scales and the future carries a basis to the cash index. When a strike is drawn on a futures chart it has been converted, and the conversion ratio, basis and observation time should be written down next to the level. The guide on GEX for ES and NQ walks through the transposition.
In Senzoukria
The GEX module has a Strikes page ("Net GEX by strike") that lists the strikes of the loaded chain with their call and put exposure, open interest per side ("OI {call} calls / {put} puts") and distance from spot ("{pct} % from spot"). The Call wall and Put wall shown on the module's overview are strikes selected from that chain. In the Option Flow feed, every print carries a Strike column and a Moneyness column so the strike can be read against the current underlying price.
Strike data reaches the desktop through the options source the user configures (Tradier, Alpaca, Market Data or Databento OPRA); the source's delay is displayed and the chain is not free market data.
Common mistakes
- Treating a strike as a resting order in the futures book. Open interest at a strike is a count of outstanding contracts, not liquidity sitting in the DOM.
- Plotting an ETF strike directly on the futures chart without converting scale and basis.
- Assuming the strike with the most open interest is also the strike with the most gamma; expiry and moneyness change the ranking.
- Reading a chain with missing strikes as if those strikes had zero open interest. A gap in the data is unknown, not zero.
Related
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Frequently asked questions
- What is the difference between a strike and the underlying price?
- The strike is fixed when the contract is listed and never changes during its life. The underlying price moves continuously. The distance between the two, together with time to expiry and implied volatility, determines the option's premium and its Greeks.
- Can a strike act as support or resistance in futures?
- A strike with large open interest or gamma is a candidate reference level, not a proven barrier. Whether price tends to slow near it under a given rule has to be measured on the converted futures level, with the observation window and the outcome defined in advance. A rejection near a strike does not identify hedging as its cause.
- Why do strikes appear and disappear from a chain?
- Exchanges add strikes when the underlying moves beyond the listed range and let sparsely traded strikes expire without relisting them. A data source can also omit strikes it did not receive. When comparing two snapshots, check that the strike coverage is the same before comparing totals.