What constitutes a 'round lot' in trading?

A 'round lot' in trading is defined as a standard trading unit of 100 shares of a security. This is a conventional benchmark used in the financial markets, which allows for standardized trading practices and facilitates liquidity in the markets. When traders refer to round lots, they are typically referring to transactions involving 100 shares, which is considered the minimum quantity for institutional trading and larger orders.

Using round lots provides several advantages, such as simplifying order processing for exchanges and helping investors compare prices and execute trades efficiently. While there are other lot sizes, such as odd lots which consist of fewer than 100 shares, a round lot is recognized as the standard measure and often carries different pricing and trading considerations, thus making it a fundamental concept in equities trading.