What is Volume / open interest (Vol/OI)?
What Is Vol/OI in Options Trading?
Updated 2026-07-21
Quick answer
Vol/OI is today’s volume divided by open interest. High ratios mean today’s trading is large versus the standing book.
Also called: Vol/OI, volume over open interest, vol oi.
Visual explainer
Vol/OI is today’s volume divided by standing open interest, a freshness ratio for screening unusual activity.
Full definition
A contract can print large absolute volume that is still normal against huge OI. Vol/OI highlights activity large versus the existing book. Use it as a “look here” flag with premium and DEX, not as a standalone trade signal.
How it shows up in TradingFlow
- Rank Contracts
Contract ranking workflows that surface activity relative to standing interest.
- Learn: Option Chain & OI
Definitions for Vol/OI and ΔOI in the tutorial series.
How to read it
- Use high Vol/OI as a “look here” flag, not a trade signal.
- Pair with premium and DEX to avoid tiny-price noise.
Who this is for
Screeners hunting fresh activity instead of chronically busy mega-contracts.
Common mistakes
- Trading every high Vol/OI print without side context.
- Comparing Vol/OI across wildly different DTE without care.
Frequently asked questions
- What is a “high” Vol/OI?
- It depends on the product. Treat Vol/OI as relative within your scanner. Extreme ratios on liquid weeklies still deserve chain and side checks.
Related terms
- Open interest (OI)Open interest is how many options contracts remain open. Unlike volume, it does not reset each morning and usually updates after the session.
- Unusual options activity (UOA)UOA flags contracts or underlyings trading far above recent norms in volume, size, or premium. It is an attention screen, not a directional signal.
- Option flowOption flow is the time-and-sales stream of options prints: contract, size, premium, and inferred aggressor side.
More guides
See the workflow in TradingFlow
Open the live Option Trades tape, rank unusual activity, and validate structure in one research path.