Open interest (OI) is the number of futures contracts that remain open. It can help describe participation in a derivatives market, but it does not show who holds each position or predict a reversal by itself. This guide explains the difference between OI and trading volume and how traders sometimes interpret them alongside price.
What open interest measures
Open interest counts matched futures contracts that have been opened and not yet closed or settled. Each open contract has both a long side and a short side. OI is counted by contract, not as a separate total for buyers and sellers.
Open interest and volume are different
OI is the outstanding balance of contracts still open at a given time. Volume measures trading activity over a particular period. A trade can contribute to that period’s volume whether it opens a new position or closes an existing one. OI changes according to whether matched trading creates new open contracts or closes existing contracts.
The core distinction is that OI counts contracts still open, while volume counts trading activity during a period.
What OI may suggest about market participation
A rising OI can indicate that more contracts remain open, while falling OI indicates that open contracts are being reduced. Neither direction identifies the participants or reveals a net long-versus-short position: every futures contract has both sides. OI is therefore a measure of outstanding activity, not proof that one group is controlling prices.
Read price, volume and OI together
Traders sometimes review these measures together. The combinations below are possible interpretations, not rules or reliable forecasts:
- Price rises, volume rises and OI rises: activity and open positioning are expanding during a rise. This may support a trend interpretation, but OI does not prove that new long positions alone are driving the move.
- Price falls, volume rises and OI rises: activity and open positions are expanding during a decline. This does not prove that short positions dominate; each contract still has a long and a short side.
- Price falls while OI falls: some open positions are closing. Depending on volume and other data, traders may interpret this as a possible weakening of the move, but it is not a confirmed bottom.
- Price rises while OI falls: positions are being reduced during a rise. The move may be losing participation, but OI alone cannot show whether the market is about to turn.
- Volume rises while OI falls: trading activity is high while the outstanding number of contracts declines. Some traders interpret this as position closing, including possible short covering or long liquidation, but the data alone cannot identify which is occurring.
OI is a supporting measure, not a reversal signal
Use OI with price structure, support and resistance, other indicators and relevant fundamental information. Avoid treating any one combination as a “100%” decision rule. OI can be misread when considered without the contract series, time period, market context and the limitations of the data.
Finding OI data on the SET site
The Thai source describes looking under SET.or.th’s derivatives or TFEX area, then trading data or statistics, and searching for series-level or daily trading statistics that include OI, volume and price. Website navigation can change; confirm the current menu and data definitions before relying on a displayed figure.
Illustrative H23 scenario
The source presents an H23 example in which prices continue to fall while OI declines, and suggests that some traders might interpret the combination as positions closing and selling pressure weakening. This is an illustration in the article, not a verified historical dataset or a prediction that a reversal will follow. Check dated exchange data before drawing conclusions.
OI can add context to futures-market analysis, but it cannot guarantee a more accurate investment decision. It should be considered with other information and a risk plan.
For a discussion about personal finances, the source article links to its LINE contact.
