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📚 Options Trading 101: Open Interest and Volume: The Liquidity Signals That Separate Smart Money from Dumb Money

Why Professional Traders Check These Numbers Before They Even Look at Price

July 13, 2025

Open Interest and Volume: The Liquidity Signals That Separate Smart Money from Dumb Money

The two data points that reveal whether you're trading in a real market or walking into a liquidity trap that could cost you thousands.

Most traders obsess over price. But when it comes to options, price is only part of the story. Hidden just below the surface are two overlooked indicators that can tell you a lot more about what’s really going on:

👉 Open Interest
👉 Volume

If you want to understand the true story behind an options contract, whether it’s liquid, whether it’s gaining attention, or whether it might offer a tradable edge, you need to know how to read both.

Let’s break them down in plain English.

What Is Volume in Options Trading?

Volume tells you how many contracts were traded today. That’s it.

It resets at the start of every trading day. If a trader buys or sells a contract, it gets counted in the day’s volume. High volume means a lot of interest right now, it’s like the heartbeat of the market.

Why it matters:

  • It tells you what traders are focused on today

  • It helps confirm price moves (if volume is high, the move might be more meaningful)

  • It can help you avoid illiquid contracts that are hard to enter or exit

Quick Tip: High volume alone isn’t enough. Always look at it in context with open interest.

What Is Open Interest?

Open Interest (OI) is the total number of contracts that are currently open, meaning they haven’t been closed or exercised.

Think of it as a tally of all the open bets on a particular option. It updates once a day, at the start of the next session.

Why it matters:

  • It shows you if an option is actively used by traders

  • High OI = strong liquidity = tighter bid-ask spreads

  • Low OI can mean illiquidity, you may get stuck in the trade

  • Rising OI = new money entering the market

  • Falling OI = traders closing out positions

📘 Example:
If you see a contract with 3,000 in volume today but OI is still only 500, most of those trades may have been opened and closed on the same day. That’s not sticky capital, it’s noise.

But if OI spikes from 500 to 1,200 tomorrow, now you know: new positions were added.

Open Interest vs Volume - What's the Difference?

Metric

Volume

Open Interest

What it tells you

Contracts traded today

Total outstanding contracts

Reset frequency

Resets daily

Updates at next day’s open

Trading signal?

Short-term focus

Longer-term interest

Why it matters

Identifies current activity

Identifies liquidity + trend in attention

How Traders Use Open Interest and Volume (with Real-World Insight)

1. Liquidity Gauge

Before you place a trade, check OI and volume. A contract with 5,000+ open interest and daily volume over 500 is generally tradable. A contract with OI under 100? Proceed with caution, the bid-ask spread will often eat you alive.

2. Identifying Unusual Activity

Surges in both volume and open interest, especially if it’s well above the norm, could signal a big trader stepping in. It doesn’t mean they’re right, but it tells you something’s happening.

3. Avoiding Traps

Many beginners chase volume spikes, thinking it must mean something. But unless those contracts stick around (in the form of rising OI), it could be nothing more than a one-day flurry.

Practical Example:

Imagine you’re looking at the AAPL $190 call, 30 days out:

  • Today’s Volume: 4,200

  • Open Interest: 800

🟡 The volume looks impressive, but that OI is still low. If OI stays under 1,000 tomorrow, that tells you most trades were intraday flips, likely not a large institutional move.

Compare that to another strike:

  • AAPL $195 call

  • Volume: 1,200

  • Open Interest: 12,000

✅ That’s the real action. More traders are holding that strike, meaning tighter spreads, better fills, and potentially more meaningful positioning.

What a Pro Would Say:

“Open interest tells me whether I’ll be able to get in and out without giving up edge. Volume tells me if there’s any heat on the strike right now. You want both, but if I had to pick one, I’d take open interest.”

Final Thought: Look for Alignment

The sweet spot for option sellers and buyers alike? When volume is surging AND open interest is rising.

That combo suggests new money is flowing in, and there’s growing conviction behind the move.

If you’re trading options without checking OI and volume, it’s like driving at night without headlights, you’re flying blind.

Want More Options 101 Lessons?

This article is part of our Options 101: First Steps to Trading series at The Option Premium, designed to build a rock-solid foundation for options traders.

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Probabilities over predictions,

Andy Crowder

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