Open interest (OI) is the total number of options contracts that are currently active — they've been opened but not yet closed, exercised, or expired. If 1,000 traders each buy one new contract and 1,000 sellers each sell one new contract, open interest is 1,000 (not 2,000, because each contract has two sides). OI updates once per day after the market closes.

Open Interest vs Volume: The Key Difference

Volume counts how many contracts traded today. Open interest counts how many contracts exist in total.

Think of it this way: Volume is foot traffic in a store. Open interest is the total inventory on the shelves.

| Metric | Measures | Updates | Resets | VolumeContracts traded todayReal-timeResets to 0 daily | Open interest | Total outstanding contracts | Once daily (after close) | Never resets (grows/shrinks) |

Example:

  • Monday: Trader A buys 10 contracts from Trader B. Volume = 10, OI = 10.
  • Tuesday: Trader C buys 5 contracts from Trader D. Volume = 5, OI = 15.
  • Wednesday: Trader A sells (closes) their 10 contracts to Trader E. Volume = 10, OI = 15 (unchanged — the contracts still exist, just new hands).
  • Thursday: Trader E sells their 10 contracts back to Trader B (who closes). Volume = 10, OI = 5 (10 contracts were closed out).

    • Why Open Interest Matters

    1. Liquidity indicator. High OI means many participants are actively involved in that contract. You'll get tighter bid-ask spreads and easier fills. Low OI (under 100) means you might struggle to enter or exit at fair prices.

    2. Market conviction gauge. Rising OI alongside a stock's move suggests fresh money is entering positions in that direction. Rising OI on calls while the stock climbs means new bulls are opening positions — a sign of conviction.

    3. Support/resistance levels. Heavy OI at specific strike prices can act as magnets or barriers. Market makers who sold options at those strikes often hedge by buying or selling the underlying stock, creating gravitational pull toward high-OI strikes — especially near expiration.

    How to Use Open Interest in Your Trading

    For buying options: Look for contracts with OI above 500 (ideally 1,000+). Higher OI means tighter spreads and easier exits.

    For selling options: High OI at the strike you're selling means plenty of counterparties. You're more likely to get filled at a fair price.

    For reading sentiment: Check the put/call open interest ratio at various strikes. Heavy call OI above the current price suggests bullish expectations. Heavy put OI below suggests hedging or bearish bets.

    The Max Pain Theory

    "Max pain" is the strike price where the total value of all outstanding options (calls + puts) would be minimized at expiration. The theory suggests stocks tend to gravitate toward max pain as expiration approaches, because market makers' hedging activity pushes the price toward this level.

    Not a reliable standalone indicator, but useful context when combined with other analysis.

    Changes in Open Interest: What They Signal

    | Price Action | OI Change | Interpretation | Stock risesOI risesBullish — new longs opening Stock risesOI fallsShort covering rally — less bullish Stock fallsOI risesBearish — new shorts opening | Stock falls | OI falls | Long liquidation — less bearish |

    Practical Screening

    When scanning for covered call or cash-secured put opportunities on OptionsPilot, filter for options with sufficient open interest to ensure you won't face liquidity problems. A good rule: sell options with at least 500 OI and place limit orders at the mid-price.

    Common Misconceptions

  • OI doesn't tell you direction. An OI of 10,000 on a call could be 10,000 buyers OR 10,000 sellers, or any mix. You need to look at how OI changes alongside price to infer direction.
  • High OI doesn't mean the option is "good." It means it's liquid. A terrible trade can still have high OI.
  • OI is backward-looking. It reflects yesterday's close, not today's activity. Volume is your real-time signal.