Mega, Large, Mid and Small Cap

The boundaries are a convention rather than a rule, and different providers draw them in different places. The ConvictionStocks screener uses mega for anything over $200 billion, large above $10 billion and up to that, mid from $2 billion up to $10 billion, and small for $2 billion and under.

The bands are useful because size travels with other characteristics. Larger companies tend to be followed by more analysts, have their shares change hands more heavily, and carry a balance sheet with room to absorb a bad year. Smaller ones tend to have fewer analysts watching, thinner trading, and a narrower set of products, so one piece of news moves the price further.

A band describes size and nothing else. It says nothing about what a company does, what is being paid for it, or how it has performed, and the course's market cap lesson is explicit that the right mix depends on the reader's own circumstances rather than on the bands themselves. The screener uses them as a filter so a list can be narrowed to companies of comparable size before anything else is asked.