A board lot is a standard number of shares trading on a stock exchange as a transaction unit. It used to be an even number earlier like 100, 200, 300 and so on as the stock exchange defined these as a round lot. This was considered to be helpful from administrative purposes and also in maintaining easy liquidity. The purpose of a board lot was also to minimize trading ‘odd lots’ like 11, 17, 19 shares and to facilitate easier trading for all stakeholders. However, electronic trading is quite efficient and has made trading and calculations related to charges, commissions etc simple. The size of a board lot does not matter much now and small retail investors/traders can buy even fractional shares easily.