A midpoint is arithmetic, not a promised fill.
Suppose a hypothetical stock quote shows a $99 bid and a $101 ask. The spread is $2 and the midpoint is $100: ($99 + $101) ÷ 2. Calculating that midpoint does not establish that a counterparty will trade with you at $100.
The bid and ask describe different sides of the quoted market. Quotes apply to a quantity and can change before an order arrives. An execution may receive price improvement, but that possibility is not a guarantee.
When reviewing a trade, distinguish the displayed quote, the benchmark you chose and the price actually filled. Label the benchmark explicitly; calling all three “the price” can hide the comparison you are trying to make.
This is an invented stock example for education, not a live quote or an order recommendation.
When you compare an execution with a quote, which benchmark and timestamp are you recording?
Sources checked October 11, 2026: Investor.gov, Bid Price/Ask Price — https://www.investor.gov/introduction-investing/investing-basics/glossary/ask-price
SEC, Trade Execution — https://www.sec.gov/investor/pubs/tradexec.htm
