Learn what a lot is in trading, why round and odd lots matter, and how trade size affects execution and liquidity.
A lot in stock and bond trading is the standard quantity unit used to describe the size of a trade.
In practice, investors often distinguish between round lots, odd lots, and other trade-size conventions depending on the market and instrument.
Lot size helps traders, brokers, and exchanges describe order quantity in a standardized way. In equities, a round lot has traditionally meant 100 shares, while smaller quantities may be treated as odd lots. In fixed-income markets, trade-size conventions can vary by issuer, market, and minimum denomination.
The concept matters because trade size can affect execution quality, liquidity, bid-ask spreads, and how easily a position can be entered or exited. A very small or unusual order may trade differently from a standard lot size.