Unusual options activity: what it is and what it is not

How unusual is usually defined

The most common test is volume against open interest. If a contract trades more contracts today than were open at the start of the day, a meaningful share of that activity is likely to be new positions, because there were not enough existing contracts to account for it through closing trades alone.

A second test compares today's volume with the contract's own average volume. Ten thousand contracts in a strike that usually trades a few hundred is unusual; ten thousand in an at-the-money SPY contract is an ordinary minute.

A third looks at premium: the dollars committed, size times price times 100. Large premium in a contract that rarely attracts it, especially in short-dated out-of-the-money strikes, is the profile most often highlighted as potentially informed.

What it can tell you

At its best, unusual activity identifies where someone has committed significant money in a way that stands out from the contract's normal pattern. When that money is paid at the ask, opens new positions and sits in short-dated contracts that need a move to pay off, it at least describes a participant with urgency and conviction.

It can also flag changes in positioning that will affect dealer hedging. A large new block of calls bought from dealers adds short gamma to dealer books at that strike, which can matter to how the stock trades as price approaches it.

In both cases, unusual activity is most useful as the start of a question: who would do this, and is it opening or closing?

What it is not

It is not proof of inside information. Large, well-timed trades do occasionally precede news, and regulators investigate those cases, but the vast majority of unusual prints have ordinary explanations. Assuming every large trade is informed means reading meaning into noise most of the time.

It is not necessarily directional. A large put purchase could be protection on a stock position. A large call trade could be one leg of a spread whose other leg is a sold call at a higher strike, or a buy-write where calls were sold against stock. A position being rolled to a later expiry generates large, unusual-looking prints in two contracts at once, neither of which is a new view.

And it is not necessarily bought. A print in the middle of the bid-ask spread cannot be classified as a buy or a sale, and a large share of the tape prints there. Calling those trades bullish or bearish is guessing.

Filtering it sensibly

The filters that help most are the ones that narrow down intent. Prints at or above the ask suggest buying; prints at or below the bid suggest selling. Volume above open interest suggests opening. Single-leg trades are easier to interpret than multi-leg ones, which are often flagged as complex orders. Repeated buying in the same contract across the day is more telling than a single print.

Context matters just as much. Activity ahead of a scheduled earnings date is expected rather than unusual. Activity in a contract that matches a large stock trade around the same time may be a hedge. And activity that agrees with the stock's own movement is more informative than activity that fights it, because price is the final arbiter of whether the money was right.

Finally, keep a record. Writing down the unusual trades you notice, with the time, price and your reading of them, and checking later what the stock did, is the only way to learn whether a particular filter carries information for the names you follow, rather than relying on memorable anecdotes.

A worked example

Suppose a mid-sized stock that normally trades a few thousand options a day sees 8,000 calls trade in a single strike two weeks out, against open interest of 600, mostly at the ask, in the first hour. That is unusual by every common definition: size far above normal, volume well above open interest, and fills that suggest buying.

Before reading it as a bet, check three things. Was there a matching trade in another strike, which would suggest a spread? Did a large block of stock print around the same time, which would suggest a hedge or a buy-write? And does the company have a scheduled event inside that expiry? If all three come back empty, the trade is what it looks like: someone opening a short-dated call position in size. That is still information about positioning, not a guarantee about the outcome.