How do I determine a particular company's market share?
A company's market share is its sales measured as a percentage of an industry's total revenues.
Determine a company's market share by dividing its total sales or revenues by the industry's total sales over a fiscal period. Use this measure to get a general idea of the size of a company relative to the industry.
Total sales (Revenues) / Industry's total sales, over fiscal period
From Investopedia
