Glossary
What is Open interest
The number of contracts still open: it rises when both sides open new positions, falls when they close, and is not the same thing as trading volume.
How it works
Example
Trader A opens a 10-contract long, trader B takes the other side: OI +10. Then A sells those 10 to a new buyer, C. OI stays at 10, while traded volume has grown to 20.
Common mistake
Reading rising OI as "people are buying": it rises when shorts open too, so OI alone does not give direction.
Read next
Related terms
Frequently asked questions
- Where can I learn Open interest step by step?
- In the Trading OS Academy: “How an exchange matches buyer and seller”.
- What is Open interest related to?
- Perpetual futures; Funding rate; Long/short ratio.
Plan versus outcome — for every trade
The Trading OS journal keeps the planned RR and the actual R of each trade side by side and computes expectancy from real results.
No sign-up: the journal runs in your browser. An account keeps your trades on the server.