What is share of voice?
Share of voice is the share of attention a brand holds in its market compared with its competitors, expressed as a percentage. In advertising it means a brand's share of all media spending in its category: a company that spends $5 million on e-reader advertising in a market where $100 million is spent in total has a 5% share of voice [1].
In SEO, share of voice means something related but different. It estimates how much of the organic search traffic available across a set of keywords goes to one site, based on where that site ranks and how many people search each keyword. A site that ranks first for a high-volume keyword earns far more share of voice than a site ranking eighth for the same term.
The idea behind both versions is the same: measure presence relative to competitors, not in isolation.
How is share of voice calculated in SEO?
SEO share of voice is calculated by estimating the clicks a site gets from each keyword it ranks for, adding them up, and dividing by the total clicks available across the whole keyword set. The steps are:
- Choose a keyword set that represents the market, for example 500 keywords a plumbing company's customers search.
- Record where each competing site ranks for each keyword.
- Multiply each keyword's monthly search volume by the expected click-through rate for the position the site holds.
- Add up the estimated clicks for each site, then divide each site's total by the total for all sites.
share of voice = estimated clicks to your site / estimated clicks to all sites in the set
estimated clicks = search volume x expected CTR at your positionThe expected click-through rate comes from a CTR curve. Published curves put the first organic result at around 28% on average, falling to under 3% at position 10: Backlinko's 2019 analysis of about 4 million results found 27.6% at position 1 and about 2.8% at position 10 [3], and SISTRIX's mobile study found 28.5% at position 1 and 2.5% at position 10 [2].
Why do SEO tools show different share of voice numbers?
SEO tools show different share of voice numbers because there is no standard formula. Each tool chooses its own keyword set, its own search volume estimates and its own CTR curve, and any of the three changes the result.
The CTR curve is the biggest source of disagreement. SISTRIX found that the click-through rate for position 1 ranges from about 13.7% on results pages with Google Shopping to 46.9% when the result shows sitelinks [2]. A tool that applies one average curve to every keyword will overstate share of voice on searches crowded with ads and shopping results and understate it on clean results pages. Advanced Web Ranking publishes a monthly CTR study from Search Console data, updated since September 2015, that now separates results pages with and without AI Overviews [4], which shows how quickly any fixed curve goes out of date.
The keyword set matters just as much. Share of voice is only a share of the keywords someone chose to track. Add 200 informational keywords where a competitor publishes guides, and that competitor's share rises even if nothing changed in the market.
What is the difference between share of voice and citation share of voice?
Share of voice measures a brand's share of estimated clicks from ranked search results, while citation share of voice measures a brand's share of the sources cited in AI answers such as AI Overviews, ChatGPT and Perplexity.
| Share of voice | Citation share of voice | |
|---|---|---|
| What is counted | Rankings, weighted by search volume and CTR | Citations inside AI answers |
| Unit | Estimated clicks | Times cited, usually once per domain per answer |
| Data source | Rank tracking across a keyword set | Prompt tracking across a prompt set |
| Main weakness | Depends on an assumed CTR curve | AI answers vary between runs |
The two can disagree. A site can rank well and win a high share of voice while rarely being cited in AI answers, or the reverse. Tracking both shows whether a brand's search presence is carrying over into AI search.
What is the difference between share of voice and a visibility index?
Share of voice is a relative percentage of a market, while a visibility index is an absolute score for one domain. A visibility index can rise for every site at once if a tool adds keywords. Share of voice always adds up to 100% across the sites compared, so one site can only gain share if another loses it.
Use a visibility index to track one site over time. Use share of voice to compare sites against each other on the same keyword set.
Where does share of voice mislead?
Share of voice misleads when it is treated as real traffic. It is a model, not a measurement. The estimate assumes every searcher clicks according to an average CTR curve, which is no longer true on results pages where ads, shopping results or other features take clicks before the organic results [2].
Three limits are worth stating plainly:
- It counts estimated clicks, not actual clicks. Search Console reports actual clicks and impressions for your own site [5], but not for competitors, so share of voice for competitors is always modeled.
- It ignores searches that end without a click. Zero-click searches still show a brand's name to searchers, but a click-based share of voice gives no credit for that.
- It is only as good as the keyword set. A small or unrepresentative set produces a confident percentage from too little data. See sample size.
No published study shows that SEO share of voice predicts revenue or market share.
How do you use share of voice well?
Use share of voice to compare the same competitors on the same keyword set over time, not as a single headline number. In practice:
- Fix the keyword set and leave it alone. Changing the keywords changes the answer, so compare months only when the set is the same.
- Segment it. Share of voice for commercial keywords and for informational keywords often tell different stories.
- Check it against real traffic. For your own site, compare the trend with clicks in Search Console [5]. If share of voice rises while clicks fall, the CTR assumptions are probably out of date for your results pages.
- Pair it with AI visibility. Track citation share of voice alongside it, since organic rankings no longer capture all of a brand's search presence.