What is the liquidity score for an option chain?
The liquidity score is a 0–100 composite that combines bid-ask spread (as a % of mid), open interest, and average daily volume on the relevant strikes to estimate how easy it will be to enter and exit the position at a reasonable price.
Formula
40% × (1 − spread%/maxSpread%)30% × min(1, openInterest ÷ 1000)30% × min(1, avgDailyVolume ÷ 500)Each scaled to 0–100.
Worked example
SPY $580 30-day call: bid 4.10 / ask 4.30 (mid 4.20, spread 4.76%). OI 12,500. Avg daily volume 2,800. Sub-scores: spread (1 - 4.76/20)% = 76; OI capped at 100; volume capped at 100. Composite = 0.4(76) + 0.3(100) + 0.3(100) = 90.
Common misinterpretation
Assuming a high liquidity score guarantees a good fill. Liquidity is a moving target. After-hours, spreads can blow out by 5×. During fast markets, fills are worse than mid by orders of magnitude.
Limitations
- OI and volume reflect end-of-day snapshots; intraday changes are not captured.
- Does not adjust for time of day or proximity to earnings/expiration.
- For deeply OTM strikes, the score can be high but the position is still illiquid in absolute terms.
Tools that use this metric
Primary references
References cite the source institution where the underlying definition or rule is published. OptionIncomeTools does not redefine standardized options terms; it ranks and presents data using widely accepted definitions.
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Educational only — not investment advice. See the disclaimer and methodology. Material methodology corrections are logged at corrections.