Open interest against volume
Volume is how many contracts changed hands today. Open interest is how many contracts are still open from every session that has ever traded this strike. Volume resets each morning; open interest only moves when positions are opened or closed. For a seller, open interest predicts whether you can get out.
They sit next to each other on every chain and they answer completely different questions. Reading one as the other is the reason people end up in a strike they cannot leave.
The two definitions
Volume counts contracts traded today. It starts at zero every morning. A single contract bought and sold four times adds four to volume.
Open interest counts contracts that exist right now, cumulative across every session. It rises when a buyer opening a new position meets a seller opening a new position. It falls when both sides are closing. It does not move at all when one party opens and the other closes, because the contract just changed hands.
Which is why a strike can trade 2,000 contracts in a day and have open interest move by 40. Most of that volume was people passing existing contracts around.
On the running chain
| Strike | IV | Bid | Ask | Mid | Delta | Volume | Open interest |
|---|---|---|---|---|---|---|---|
| $36 call | 41.0% | $3.60 | $3.75 | $3.67 | 0.711 | 214 | 3,118 |
| $37 call | 39.6% | $2.93 | $3.05 | $2.98 | 0.646 | 331 | 2,004 |
| $38 call | 38.4% | $2.32 | $2.41 | $2.36 | 0.573 | 1,207 | 6,442 |
| $39 call | 37.4% | $1.80 | $1.87 | $1.83 | 0.495 | 688 | 3,975 |
| $40 call | 36.6% | $1.35 | $1.41 | $1.38 | 0.416 | 2,946 | 22,107 |
| $41 call | 35.9% | $1.00 | $1.05 | $1.02 | 0.339 | 402 | 2,687 |
| $42 call | 35.3% | $0.71 | $0.76 | $0.73 | 0.268 | 1,015 | 9,204 |
| $43 call | 34.8% | $0.49 | $0.53 | $0.51 | 0.205 | 77 | 1,388 |
| $44 call | 34.4% | $0.33 | $0.38 | $0.35 | 0.153 | 12 | 640 |
| $45 call | 34.1% | $0.21 | $0.26 | $0.23 | 0.111 | 843 | 5,412 |
Three rows are worth stopping on.
$40 call: 2,946 traded, 22,107 open. The busiest line on the chain by both measures. There is a real market here, a tight nickel-wide quote, and you will be filled in seconds. It is also 0.416 delta, which is a lousy strike for a covered call seller. Liquidity and merit are different columns.
$44 call: 12 traded, 640 open. Nobody is here. The market is five cents wide on a 35 cent option, which is 14.3 percent, and that is because a market maker is quoting into an empty room. You can sell it. Getting out at a sane price later is the problem.
$45 call: 843 traded, 5,412 open. Heavy volume relative to what is standing there. Something happened at that strike today, probably somebody rolling into it or opening size. Volume out of proportion to open interest is the signal that a position is being built or unwound right now.
The stale column
Open interest is not live. It is computed by the clearing house from overnight processing and published once, before the next session opens. The open interest number you are looking at during the trading day is yesterday's, and nothing you do today shows up in it until tomorrow morning.
Volume, meanwhile, is intraday and updates as trades print.
So on a strike that got busy this morning, the two columns are describing different days. That is not a bug in your platform. It is worth knowing before you conclude that a strike with 40 open interest and 3,000 volume is illiquid.
What a seller does with them
Open interest is a liquidity filter, and it belongs in the same pass as the bid-ask spread rather than in the strike decision.
The order that works: find your delta band, then check that the strikes in it have enough open interest and a tight enough quote to be worth trading. If the good delta lives at a dead strike, the trade is on a different ticker. Cluster H sets hard thresholds for this and its finding is worth the trip: on a 60-name screen the liquidity filter alone removed about two thirds of the field.
Rough floors for a retail-sized position, from the same page: open interest in the high hundreds at minimum, a spread inside 10 percent of the mid, and some volume today rather than none. The $44 call here fails two of the three.
Three things open interest does not tell you
Direction. Every open contract has a buyer and a seller. Twenty two thousand contracts at the $40 strike is not twenty two thousand bulls. There is no way to read sentiment off this column and the people who claim otherwise are guessing.
Whether the strike is good. Covered here twice because it is the mistake that keeps happening. Round numbers accumulate open interest because people think in tens.
What will happen at expiry. Large open interest at a strike near the money gets talked about as a magnet, and the theory around it is not something this page is going to assert. What is real and mechanical is pin risk on your own position when the stock finishes within a cent of your strike, and that has nothing to do with how many other contracts are open there.
OptionsKing scores every candidate strike on a deterministic 0 to 100 scale, blends that score with the return on the capital the trade ties up, and shows you the highest-ranked handful. There is no minimum score. How it works covers what the ranking does and does not tell you.
Questions people actually ask
What is the difference between volume and open interest?
Volume counts contracts traded today and resets each morning. Open interest counts contracts still outstanding from every session, and only moves when positions are opened or closed rather than passed between traders.
Is open interest updated in real time?
No. It is computed by the clearing house from overnight processing and published once before the next session opens, so the figure you see during the day is yesterday's. Volume is intraday and updates as trades print.
How much open interest should a strike have before I sell it?
For a retail-sized position, a floor in the high hundreds, plus a spread inside about 10 percent of the mid and some volume today. On the worked chain the $44 call has 640 open, 12 traded and a 14.3 percent spread, and fails on two of the three.
Does high open interest mean the strike is bullish?
No. Every open contract has a buyer and a seller, so the column carries no directional information at all. High open interest usually means a round number that attracted positions.
Sources
Rules and thresholds above were checked against these documents on August 4, 2026. Exchange and broker rules change. Confirm anything you are about to act on with your own broker.
Keep reading
Do the math on your own trade
Every price in this article is an illustrative worked example, not a quote. Read Options basics for the rest of the series, and the disclaimer before you act on any of it. Selling options carries real risk of loss, and the loss can be far larger than the premium you collected.