Liquidity screening, and what to reject

Liquidity decides whether the premium a screen shows you is a price you can get. Three numbers do the work: open interest tells you whether a market exists, the day's volume tells you whether anyone is there now, and the bid-ask spread tells you what showing up costs. On one screen those three dropped 147 candidates to 41.

A screener quotes the mid. The mid is the average of two prices, and it is not necessarily either of them.

The candidate that made the point

PARA at $11.20 with a $12.50 call, 45 days out, 46 percent implied volatility. The screen's mid was $0.30, which on an $11.20 stock is 21.7 percent annualized. Best return on the whole list at that stage, by a distance.

The market on that contract was $0.20 bid at $0.40 ask.

Sell into the bid, which is what you get when the other side is one market maker with no competition, and the credit is $20, not $30. Annualized return: 14.5 percent. A third of the trade evaporated between the screen and the fill, and nothing went wrong.

Then think about closing it. You are buying back at the ask on a contract nobody trades. The round trip on that spread is $0.20, which is two thirds of the mid you were originally quoted.

The three numbers

Open interest. Contracts outstanding at that strike, updated overnight, so today's figure is yesterday's. It tells you whether a market has ever existed here. Low open interest with real volume is a new strike getting attention. High open interest with no volume is a graveyard: those contracts were opened, everyone is sitting on them, and nobody is trading them today.

Volume. Contracts traded so far today. Live, and noisy, and zero for most strikes most mornings. Its value is confirming that open interest is not stale.

Spread. The distance between bid and ask, best read as a percentage of the mid. This is the only one of the three you pay directly, and it is the one to weight if you weight any of them.

Neither of the first two matters on its own. Together they tell you whether you can get out.

Thresholds, and what each one caught

The thresholds this screen used, and why each one is where it is.

• Open interest at least 500. Enough that a market maker will quote it and enough that you are not the only person who has ever held this contract. Below 100 you are negotiating with one participant.
• Volume at least 25 today. Deliberately low. It is a pulse check, not a popularity contest, and demanding hundreds would cut you down to the twenty most crowded names on the exchange.
• Spread no wider than 15 percent of the mid. The one that does the damage, and the one worth arguing about. It dropped 33 contracts on this run, more than open interest and volume put together.

These are conventions, not laws. A 15 percent spread on a $0.60 option is 9 cents, and on a $6 option it is 90 cents, which is a different animal. If you sell cheap options, add an absolute cap: no wider than $0.10, whatever the percentage says.

What passing actually means

Look at the CSCO row. It passed, and its spread is 12.9 percent of the mid.

That is not a tight market. It is an acceptable one, and the difference matters. Selling that call at the bid rather than the mid costs $4 per contract, and doing it eight times a year costs $32 against roughly $496 of annual credit. Six and a half percent of your income, priced out in full, on a contract that cleared the filter comfortably.

Compare XOM at 3.8 percent. Same screen, same day, and one of them charges you three times as much to trade.

Where liquidity goes when you need it

The reason to care is not the entry. You choose when to enter and you can walk away from a bad market.

You do not choose when you need to exit. Spreads widen exactly when everyone wants the same side: after a gap, on an earnings day, in the last hour of expiration Friday, in a selloff. A contract quoting $0.58 at $0.66 on a quiet Tuesday can quote $0.90 at $1.60 the morning after a downgrade, and that is the morning you wanted to close it.

So screen the entry for the exit you have not had yet. A name that is thin in calm weather is untradeable in bad weather, and the bad weather is the entire reason you would be trying to trade.

The shortcut that mostly works

Liquidity in single-name options follows the underlying. Big, heavily traded, widely held stocks have tight chains; small caps and recent listings do not.

So most of the work is done by the universe you screen rather than the filters you apply, and a list of 60 genuinely liquid names with a 15 percent spread cap will beat a list of 3,000 tickers with elaborate liquidity scoring. Fix the universe first. It is less work and it fails less often.

OptionsKing scores every candidate strike on a deterministic 0 to 100 scale, blends that score with the return on the capital the trade ties up, and shows you the highest-ranked handful. There is no minimum score. How it works covers what the ranking does and does not tell you.

Questions people actually ask

Sources

• Black and Scholes (1973), Journal of Political Economy 81(3), 637 to 654
• OCC, Characteristics and Risks of Standardized Options

Rules and thresholds above were checked against these documents on August 4, 2026. Exchange and broker rules change. Confirm anything you are about to act on with your own broker.

Keep reading

• What an acceptable spread costs over a year
• Getting the mid you were quoted
• Where this filter sits in the funnel

Do the math on your own trade

• Covered call calculator premium, break-even, static and if-called return, annualized.
• Assignment probability calculator delta to keep-odds, with the caveat that matters.
• Annualized return calculator turn any credit and any holding period into a yearly rate.

Every price in this article is an illustrative worked example, not a quote. Read Screening and probability for the rest of the series, and the disclaimer before you act on any of it. Selling options carries real risk of loss, and the loss can be far larger than the premium you collected.