Home › Volume vs open interest
Volume vs open interest
Volume counts how many contracts traded today. Open interest (OI) counts how many contracts remain open — not yet closed, exercised or expired. OI is typically calculated after the close and published the next trading day.
| Volume | Open interest | |
|---|---|---|
| What it counts | Contracts traded today | Contracts still open |
| Resets | Every day | Never — it accumulates and declines |
| Updates | During the session | Once a day (next morning) |
How a trade changes open interest
| Buyer is… | Seller is… | Effect on OI |
|---|---|---|
| Opening | Opening | + increases |
| Opening | Closing | No change |
| Closing | Opening | No change |
| Closing | Closing | − decreases |
Why “volume greater than open interest” gets attention
If today's volume in a contract is larger than all the open interest that existed this morning, at least some of that volume must be new positions. That's why many screens flag a high volume-to-OI ratio as “unusual.”
Confirm the next day
Check the next morning's OI. If it rose by roughly the size of the trade, the position was likely opened and held overnight. If OI barely moved, the activity may have been day trading, or opening and closing trades offset each other.
Example (illustrative numbers only): a contract opens the day with 1,000 OI and trades 6,000 contracts. If tomorrow's OI is about 6,500, much of today's volume stayed open. If it's 1,200, most of it didn't.