Market share is a company's sales divided by the total sales of its market, as a percentage: one number about the company, from research or an industry body. Distinct from share of wallet, which is one number per customer and rolls up. The two can move in opposite directions.
Market share is the percentage of a market's total sales that one company makes, in dollars or in units, over a stated period, category and geography. To calculate market share, divide the company's sales by total market sales and multiply by 100.
Market share is a board and marketing figure. Share of wallet is the one that produces a list per rep.
Adding small new customers raises market share while wallet share at the existing base falls. Only the second shows the leak.
Market share % = company sales ÷ total market sales × 100, both in the same category, geography and period. Revenue share uses dollars; unit share uses units sold. Total market sales come from research or an industry body.
A brand sells $40 million in a category measured at $500 million: $40 million ÷ $500 million × 100 = 8 percent. It says nothing about which customers could buy more, which is what share of wallet measures.
Confused with share of wallet. One is about the market; the other is about each customer.
For the difference in practice, see share of wallet versus market share.