Model the Flows · Lesson 6 of 9

Reading Options Flow

Sweeps, blocks, opening and closing trades, spreads and hedges: what a single options print can and can’t tell you.

7 min readAdvancedModule 2: Model Risk and JudgmentUpdated Oct 8, 2026

In this lesson

Tell a sweep from a block and say what each one shows
Explain why one print rarely reveals whether it opened or closed a position
Spot multi-leg trades and hedges that look directional one leg at a time
Use flow as a record of activity, not a read of intent

Options flow is the stream of individual options trades: the contract, size, price, time and whether each one printed nearer the bid or the ask. Two numbers usually sit beside each print. Premium is the cash that changed hands (price × contracts × 100). Notional is the value of the shares the contracts control (contracts × 100 × stock price), which is usually far larger and isn’t the money that changed hands. Neither number alone tells you how much anyone can lose. It’s tempting to read every large print as someone placing a smart bet. The habit that keeps you out of trouble is simpler: flow shows activity, not intent. The size and price are facts. The reason behind them is a guess.

Sweeps and blocks

Sweep

One order split across several exchanges at once, taking the size available at each price (sweep)
Often read as urgency: someone wanted it filled now rather than at a better price
Can come from any account whose broker routes an order this way, not only large funds
Shows speed, not why: a hedge can be just as urgent as a bet

Block

One large trade printed as a single transaction (block trade)
Often arranged in advance and crossed at one price, sometimes between the bid and the ask
Common for institutions and for the legs of larger structures
Shows size, not direction: the other side of a block is exactly as large

Where a trade printed adds a clue. At or near the ask suggests the buyer started the trade; near the bid suggests the seller did; in the middle, it’s unclear. Even a clean ask-side print isn’t automatically bullish. Someone buying calls at the ask might be opening a new bet, or buying back calls they sold last month. Multi-leg orders add another wrinkle: they trade at one net price for the whole package, so a single leg can print at a price that looks odd on its own. Whether a trade opened or closed a position (opening vs closing trade) decides which story is true, and a single print rarely tells you.

Example Consider this example

A hypothetical stock trades at $200. Yesterday, its $210 call expiring in 30 days had open interest of 2,000 contracts. Today 5,000 trade, mostly at the ask near $2.50: about $1.25 million in premium (5,000 × $2.50 × 100) controlling $100 million of stock (5,000 × 100 × $200). Volume that far above yesterday’s open interest usually means new positions were opened, though contracts opened and closed within the same day make any exact count impossible. If tomorrow’s open interest reads 6,200, that’s a net increase of 4,200. You still don’t know who opened, which side they took, or why.

One leg can mislead

Spreads. 2,000 calls bought and 2,000 higher-strike calls in the same expiration sold in the same second likely form a vertical spread. Reading only the bought leg overstates how bullish the trade is.
Collars and risk reversals. A fund that owns stock may buy puts and sell calls at the same time. Both legs look bearish on a tape; together with the shares they form a collar, which limits losses on stock already owned. The same two legs without stock are a risk reversal, a bearish bet. The tape alone can’t tell you which one you’re seeing.
Hedges. A big call purchase can protect a short stock position, a single-stock put buyer may be protecting shares ahead of earnings, and index puts are often portfolio insurance rather than a bet on a crash.
Rolls. A roll closes one expiration and opens the next, which prints two large trades that together only extend an existing position. Rolls tend to cluster in the days before a big expiration.
Dealer and arbitrage trades. Market makers offset risk and run trades that pair options with stock to lock in small pricing differences. They can print huge size with no view on direction at all.

Is it one leg or several?
Look for matching size and time stamps on other strikes, other expirations or the stock itself. Many flow tools tag multi-leg trades, but not all of them.
Where did it print?
At the ask, at the bid or in the middle. The side hints at who started the trade, not whether it opened or closed a position.
How big is it, really?
Compare the size with that strike’s open interest and its normal daily volume. 500 contracts is huge in a thinly traded stock and routine in SPY. Volume well above the prior day’s open interest is a common reason a print gets flagged as unusual.
When does it expire?
A same-day, out-of-the-money print is a short-lived position whose influence fades by the close. A block in an expiration months away may sit untouched for weeks. The same premium can mean very different things.
Did open interest confirm it?
The next morning’s change shows whether positions grew or shrank on balance, though not who added them. If open interest rises by roughly the size of the print, an opening trade is likely; if it barely moves, the print may have closed positions or been offset by other trades.
How does it touch the map?
Opening trades reach open interest only the next day. Intraday Build-up comes from price and time re-pricing the gamma of last night’s open interest, so it doesn’t show new positions. Heavy customer call buying can also cut against the dealer-side sign assumption.

Watch out Following prints isn’t a plan

The trader behind a print may hold a hedge you can’t see, a far larger account and a different time frame. They may also be wrong: large traders lose on positions too, and you’ll never see their exit. If a print catches your eye, write your own plan with your own invalidation and size, as if the print had never happened.

Key takeaways

Flow shows activity, not intent: size, price and time are facts, and the reason is a guess.
Sweeps show urgency and blocks show size; neither shows direction on its own.
Check for spreads, collars, rolls and stock hedges before reading one leg as a bet.
Opening versus closing is rarely clear from one print; the next day’s open interest gives clues.

Try it in StratosHedge

Open Vol & Flow, pick one large print, and write down what you can verify (size, price, side) and what stays unknown (opening or closing, intent). Tags such as Sweep, Opening or Multi-leg, and the bullish and bearish premium totals, are the data provider’s inferences, not known intent.

Read a print in Vol & Flow Needs: Advance plan

Key terms

Options flow: The stream of individual options trades, with size, price, time and an estimate of whether each traded nearer the bid or the ask.
Print: The public record of a trade that has executed, showing its price, size and time. It doesn’t show who started the trade or why.
Sweep: An order that fills across several exchanges at once, taking available size at successive prices. Traders often read it as urgency.
Block trade: One very large trade, traditionally 10,000 shares or more, often negotiated privately and printed as a single transaction.
Opening vs closing trade: Whether a trade starts a new position or exits an existing one. A single print rarely tells you; the next day’s open interest change gives clues.
Vertical spread: Buying one option and selling another of the same type and expiration at a different strike. Both the maximum gain and maximum loss are capped.
Roll (a position): Closing an option position that is about to expire and opening a similar one in a later expiration, often at a new strike.

Sources and further reading

Educational content, not investment advice. Lessons describe how markets and models tend to behave. They don’t tell anyone what to buy, sell or hold. Interactive examples use illustrative sample data, and simulator results are simulated — not actual trading. Options involve risk and are not suitable for all investors.

Risk disclosure Characteristics and Risks of Standardized Options (OCC) (opens in a new tab)

Reading Options Flow

In this lesson

Sweeps and blocks

Sweep

Block

One leg can mislead

Check your understanding

Key takeaways

Try it in StratosHedge

Key terms

Sources and further reading

Data intelligence.
Visualization with context.

In this lesson

Sweeps and blocks

Sweep

Block

One leg can mislead

Check your understanding

Key takeaways

Try it in StratosHedge

Key terms

Sources and further reading

Data intelligence.Visualization with context.

Data intelligence.
Visualization with context.