Volume and Open Interest: What They Actually Tell You
Futures give you a data point equity traders do not get: open interest. Volume tells you what happened today; open interest tells you how many positions are still standing. The pair together is the closest thing to a positioning read available for free.
The definitions
| Volume | Open interest | |
|---|---|---|
| Counts | Contracts traded today | Contracts currently open |
| Resets | Every session | Never — it accumulates |
| What it shows | Activity | Commitment |
| Rises when | Any trade, opening or closing | A new buyer and a new seller both enter |
The key mechanic: open interest only rises when a new long meets a new short. If an existing holder closes and someone else takes the other side, open interest falls or is unchanged — even though volume was recorded.
The four combinations
| Price | Open interest | Reading | Strength |
|---|---|---|---|
| Up | Up | New money entering long — trend supported | Strong |
| Up | Down | Short covering — rally has no new buyers | Weak |
| Down | Up | New money entering short — decline supported | Strong |
| Down | Down | Long liquidation — selling is exhausted supply | Weak |
The most misread cell is the second row. A rally on falling open interest is shorts being forced out, not buyers arriving. It ends when the shorts are done.
Three limits you need to know
1. Open interest is reported with a one-day lag
Exchanges publish open interest after the close for the previous session. You are always looking at yesterday's positioning. Intraday, only volume is real-time.
2. Roll weeks distort everything
During a roll, open interest drops in the front month and rises in the next. That is bookkeeping, not positioning. A 20% fall in front-month open interest in the last week before expiry is normal and means nothing.
3. It tells you nothing about direction, only participation
Open interest is symmetric — every long has a short. Rising open interest says both sides are committing, not which side is right.
Where to get the data
- Exchange daily bulletins — CME, ICE and Eurex publish volume and open interest per contract each session
- The COT report — the CFTC's Commitments of Traders, released Friday for Tuesday's positions, breaks open interest into commercial, non-commercial and non-reportable categories
- Your platform — most charting packages show volume by default and open interest as an optional series
The COT report is the only free window into who holds the positions. It is three days stale when published, which makes it a context tool, not a signal.
Using it without overfitting
Volume confirms that a move had participation; open interest confirms whether that participation is new money or position closing. Beyond that, both are descriptive. Strategies built on "volume spike means reversal" or "open interest divergence predicts tops" have been tested extensively and do not hold up as standalone edges — the honest use is sizing confidence in a move you already have a reason to take.
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