Two sides, one contract count
Every outstanding contract has a long and a short side. Open interest counts the contract once, not separately for buyer and seller. Our period volume also counts each matched contract once.
All numbers below are fictional. Consider one expiry of one hypothetical future, initially 100 contracts outstanding. Delivery, expiry, changes between maturities and other adjustments are excluded.
Three transaction types change the stock differently
First, buyers open longs and sellers open shorts: 40 new pairs add 40 volume and 40 open interest. Next, 25 short positions are bought back against closing longs: another 25 volume, but open interest falls 25.
Finally, new buyers open 15 longs while existing long holders close 15. The holder changes but the contract remains outstanding: volume rises 15 and open-interest change is zero. These are grouped contract quantities, not counts of individual orders.
| Group | Volume | OI change | OI balance |
|---|---|---|---|
| Both sides open | 40 | +40 | 140 |
| Both sides close | 25 | -25 | 115 |
| Opening against closing | 15 | 0 | 115 |
Check flow and stock independently
Period volume is 40+25+15=80 contracts. Ending open interest is 100+40−25=115. The outstanding stock changes only+15 despite 80 contracts trading.
Total volume 80 alone cannot recover the split between opening, closing and position-transfer transactions. A chart’s volume bar does not supply that missing classification.
| Measure | Contracts |
|---|---|
| Initial open interest | 100 |
| Period volume | 80 |
| Open-interest change | 15 |
| Ending open interest | 115 |
Report date and status matter
For a real comparison record contract, expiry, venue, trading date and release time. CME distinguishes the preliminary daily report from the official next-morning bulletin; the figures can differ. Label them before comparing.
Increasing open interest does not make the entire market “net bullish”: each long has a short counterpart. This balance does not establish future direction, participant intentions or cash inflow.
Change one set of transactions
Starting from 100, 20 new pairs open and 10 pairs close, with no other events. What are volume and ending open interest?
Answer: volume 20+10=30; change+20−10=+10; final stock 110. Counting long and short sides separately would double-count the same contract.
Do not invent a product field
Student Wyckoff can show source-provided volume for closed bars. Open interest availability in the product is unconfirmed; this article does not promise an OI panel. Use a separate official exchange report for that measure.
- Match the same contract and date.
- Record preliminary or official status.
- Separate available volume from unknown open interest.
Primary sources
Sources explain the mechanics and limitations; the editorial examples use invented numbers rather than market quotations.
Your next practical step
Check the available volume units in the guide and compare neighbouring closed bars. Consult a separate exchange report for open interest; no such platform panel is promised.
Explore the available volume guide ↗