Market share

Market share is the percentage of total sales in a market or category captured by a specific company, product, or brand. It measures actual performance relative to the market, distinct from total addressable market, which measures the theoretical opportunity regardless of who captures it.

It's calculated as market share = company's sales in the category / total sales in the category, over the same period and market definition, and can be measured in revenue (value share) or units (volume share) — the two can tell different stories, since a company can gain unit share while losing value share if it competes mainly on price.

Market share trends are one of the clearest signals of competitive standing, feeding directly into competitive intelligence and strategic reviews such as a SWOT analysis. The figure is highly sensitive to how the market is defined: a narrow category definition inflates a company's apparent share, while a broad one dilutes it, so figures from different sources are often not directly comparable unless the market definition and time period are stated and matched. It's related to but distinct from share of wallet, which measures the share of an individual customer's spending rather than the whole market's.