Market share is the percentage of the total market (or industry) sales made by one firm. Market share can be reflected as either a percentage of sales dollars, a percentage of units sold, or a percentage of customers. Percentage of sales dollars is the most common reference.
The market share for particular brands/products can be found in the database Business Insights: Global. Once in the database, hover your cursor over the Industries tab and click on Market Share Reports:
Type the name of your brand/product into the search box and hit search/enter: