Formula
Brand mentions or impressions / Total category mentions or impressions x 100
How to measure
Aggregate mention or impression counts for the brand and its main competitors across the same channels and time window, then calculate the brand's percentage share.
Why track it
Share of voice contextualizes brand growth against the competitive landscape, since absolute awareness numbers can rise while relative position still falls.
Example
A challenger brand grows its share of voice from 8% to 15% of category conversation after a major campaign, even as the market leader's total mentions also grow.