Quoted Spread
Quoted spread is the displayed bid ask spread at a moment in time: best ask minus best bid. It is a quote based measure, not fill based.
Definition
Quoted spread is the spread you see on screen at a specific moment: the best ask minus the best bid.
Formula: QS = best ask - best bid
Why it matters
Quoted spread is a quick snapshot of transaction cost and market tightness. It is useful for comparing markets, but it does not guarantee your execution will happen at those prices.
Quoted spread vs effective spread
Effective spread is computed from your actual fill relative to the midquote. Quoted spread is based on displayed quotes, not on fills.
Common pitfalls
Stale snapshot: The quoted spread can change between the time you observe it and the time you trade.
Hidden cost: Even with a tight quoted spread, thin depth can cause slippage and worse fills.