Most sellers judge their PPC account on one number: ACoS. If it's low, the account "looks healthy." If it spikes, panic sets in and bids get slashed. But ACoS is a backward-looking snapshot of what happened on one campaign over a chosen date range — it says nothing about whether you're actually winning your category, or quietly losing it to a competitor who is happy to run a slightly higher ACoS to take the shelf space you're giving up.
Share of Voice (SOV) is the metric that answers the question ACoS can't: out of all the ad impressions available for your most important keywords, what percentage are you actually capturing — and how does that compare to your competitors? At StoreStride we track Share of Voice for every brand we manage alongside ACoS and TACoS, because an account can hit every efficiency target on paper while steadily losing category position in the real auction.
A "healthy" ACoS can hide a shrinking business. If you cut bids to protect ACoS while a competitor holds firm, your Share of Voice drops, your organic rank follows it down within weeks, and the business you're protecting on paper is the one actually losing ground in the market.
What Is Share of Voice on Amazon?
Share of Voice measures what proportion of available ad impressions (or, in a more advanced form, estimated search impression share) for a given keyword your brand is capturing, versus every other seller bidding on that same term. If a keyword generates 100,000 impressions a month across Sponsored Products and Sponsored Brands placements, and your campaigns are responsible for 15,000 of them, your Share of Voice on that keyword is 15%.
It is a category-level, competitive metric — not an account-level efficiency metric. ACoS tells you what a click cost relative to the sale it generated. Share of Voice tells you how much of the battlefield you actually occupy, regardless of how efficiently you occupy it.
Share of Voice vs ACoS: Why They Tell Different Stories
These two metrics can move in completely opposite directions, and understanding why is the whole point of tracking both.
📉 Low ACoS, Low Share of Voice
Bids are conservative, every click that converts looks efficient on paper, but overall impression volume on your core keywords is a fraction of what's available. You're profitable on the clicks you get — and invisible for most of the searches that matter. Competitors with a higher ACoS tolerance absorb the impressions you're leaving behind.
📈 Higher ACoS, High Share of Voice
Bids are set to win a meaningful share of top-of-search placements on priority terms. ACoS runs higher than the "comfortable" number, but the brand is visible for most of the category's search volume, which feeds organic rank, review velocity, and repeat purchase — compounding returns ACoS alone never captures.
Neither posture is automatically correct. The point is that a seller who only watches ACoS has no way to tell which situation they're in. A seller who also tracks Share of Voice can see immediately whether a "good" ACoS is the result of smart bidding or of simply not showing up.
How to Calculate Your Share of Voice
Amazon doesn't hand you a single "Share of Voice" number in Seller Central, so you build it from data you already have access to.
Simple formula: Share of Voice = (Your impressions on a keyword ÷ Total available impressions on that keyword) × 100. Pull your own impression counts from the Sponsored Products and Sponsored Brands search term reports for your priority keywords. Estimate total category impressions using a third-party rank tracker (Helium 10, Perpetua, or similar tools that track top-of-search presence across all sellers for a given term), or by manually tracking how often your brand appears in the top rows of search results for that keyword over a sample period.
For a faster, directional version that doesn't require third-party tools, track top-of-search placement frequency: over 20–30 searches of your most important keyword spread across different times of day, how often does your brand appear in the first row of sponsored results? If it's 6 out of 30, your practical Share of Voice for that term is roughly 20% — and you now know exactly which keyword needs budget.
Why Share of Voice Predicts Growth Better Than ACoS
ACoS is reactive — it reports what already happened. Share of Voice is a leading indicator because Amazon's ranking algorithm rewards sustained visibility and sales velocity on a keyword over time. A brand that holds a strong Share of Voice on its core terms tends to see three compounding effects that a low-ACoS, low-visibility strategy never generates:
- Organic rank climbs as sustained ad impressions and clicks feed the same relevance signal Amazon uses for unpaid search results
- TACoS improves over time even if ACoS doesn't, because a growing share of total sales shifts from paid to organic as rank improves
- Competitor pressure drops because sellers with a strong, consistent presence on a keyword are harder and more expensive for new entrants to dislodge
None of this shows up in a weekly ACoS report. It only becomes visible when you track Share of Voice over months, not days.
The Levers That Actually Move Your Share of Voice
Improving Share of Voice isn't just "bid higher everywhere." It's a deliberate set of choices concentrated on the keywords that matter most to the category you're trying to win.
Building a Share of Voice Strategy: Step by Step
Identify Your 10–15 Category-Defining Keywords
These are the high-volume, high-intent terms that define your category — not every keyword you rank for. Pull them from your search term reports and Brand Analytics search frequency rank data.
Benchmark Current Share of Voice on Each
Use a rank tracker or manual top-of-search sampling to establish a baseline for where you stand today against your main competitors on each keyword.
Set a Target Share, Not Just a Target ACoS
Decide what percentage of impressions you want to hold on each priority keyword over the next quarter, and treat ACoS on those specific keywords as a secondary, monitored metric rather than the primary control.
Allocate Budget and Bids to Match the Target
Fund your Share of Voice keywords first, with dedicated campaigns or portfolios, before spreading remaining budget across the long tail of smaller terms.
Re-Measure Monthly and Track the Trend
Share of Voice moves slowly compared to ACoS. Review it monthly alongside organic rank and TACoS to see whether your investment is converting into real category position, not just impressions.
When a Lower Share of Voice Is the Right Call
Not every keyword deserves the same fight. On low-margin, highly competitive terms where the cost to win meaningful Share of Voice would exceed what the category is worth to your brand, a conscious decision to run lower visibility and protect margin is entirely reasonable. The goal is not maximum Share of Voice everywhere — it's deliberate Share of Voice on the keywords that actually drive your business, and a clear-eyed choice to concede ground elsewhere.
Not sure where you actually stand in your category?
StoreStride benchmarks Share of Voice against your real competitors as part of every account audit, alongside ACoS and TACoS — so decisions are based on category position, not just last week's spend. Get a free audit of your account.
Get Free Amazon PPC Audit →Common Questions About Share of Voice
Does Amazon show Share of Voice directly in Seller Central or Advertising Console?
Not as a single labelled metric. You build it from your own impression data in the Sponsored Products and Sponsored Brands search term reports, combined with category-wide estimates from a third-party rank tracker, or from manual top-of-search sampling for your priority keywords.
How often should I review Share of Voice?
Monthly is usually sufficient, since it is a slower-moving, trend-based metric. Reviewing it weekly alongside ACoS tends to create noise rather than insight — small daily or weekly swings in impression share are normal and don't indicate a real shift in category position.
Should every seller prioritise Share of Voice over ACoS?
No. Share of Voice matters most for brands competing in a visible, defensible category where organic rank and repeat purchase compound over time. For sellers in extremely thin-margin or highly commoditised categories, disciplined ACoS control may reasonably take priority. The right approach is to track both and understand which one is driving decisions at any given time.
Can a small seller compete on Share of Voice against larger, better-funded brands?
Yes, if the keyword set is chosen carefully. Rather than competing for Share of Voice on the broadest, most expensive category terms, smaller brands often win more sustainable Share of Voice on narrower, higher-intent long-tail variations where larger competitors are spreading their budget too thin to dominate.