Definition
Share of Market (SOM) is a metric that represents the proportion of total sales in a defined category, market, or segment that is captured by a particular brand, product, or company over a given period. It indicates how large a brand’s commercial footprint is compared with its competitors.
In marketing, SOM is a core indicator of competitive position and growth. It shows whether a brand is gaining or losing relevance in the category in concrete commercial terms, regardless of how much media it runs or how visible its campaigns appear. SOM is often paired with Share of Voice (SOV) and other leading indicators to understand whether marketing activities are translating into business outcomes.
How Share of Market (SOM) relates to marketing
SOM connects brand and marketing efforts directly to business performance:
- It provides a clear view of competitive standing: who leads, who is catching up, and who is falling behind.
- It acts as a lagging indicator for marketing effectiveness, reflecting the cumulative impact of product, price, distribution, and promotion.
- It guides marketing strategy decisions around investment levels, positioning, and channel focus.
For marketing leaders, SOM helps answer questions such as:
- Are our campaigns and product efforts resulting in real gains in the category?
- Is growth coming from category expansion, competitor switching, or specific segments?
- Are we defending our existing position effectively, or eroding over time?
How to calculate Share of Market (SOM)
The basic formula for SOM is:
Share of Market (SOM) = (Brand sales ÷ Total category sales) × 100
You can define “sales” and “category” in different ways, depending on the business question.
Revenue-based SOM
SOM (by revenue) = (Brand revenue ÷ Total category revenue) × 100
Example:
- Brand revenue in a quarter: $50M
- Total category revenue in that quarter: $500M
- SOM = (50 ÷ 500) × 100 = 10%
Volume-based SOM
SOM (by volume) = (Brand units sold ÷ Total category units sold) × 100
Useful in categories where unit volume is a better indicator than revenue (e.g., commoditized goods, usage-driven products).
Segmented SOM
You can calculate SOM within specific dimensions:
- Geography (e.g., SOM in North America vs. EMEA)
- Channel (e.g., SOM in e-commerce vs. retail)
- Segment (e.g., enterprise vs. SMB, premium vs. value tiers)
The formula remains the same; you just narrow the numerator and denominator to the relevant segment.
SOV–SOM comparison
SOM is frequently compared with SOV to assess whether marketing effort aligns with business position:
- SOV > SOM: brand is “over-speaking” its current share and may be investing for growth.
- SOV < SOM: brand risks under-supporting its position over time.
How to utilize Share of Market (SOM)
SOM is used widely in strategic and operational marketing decisions.
Market and portfolio strategy
- Identify whether you are a leader, challenger, or niche player in each category.
- Decide where to defend, grow, or de-prioritize based on SOM trajectory.
- Assess the relative importance of categories or segments in the overall portfolio.
Marketing investment and planning
- Use SOM alongside SOV to shape budget levels:
- Brands seeking growth often target SOV at or above SOM.
- Mature leaders may decide to maintain moderate SOV to defend existing SOM.
- Track whether increases in marketing investment are followed by SOM improvements over relevant time horizons.
Category and segment prioritization
- Compare SOM across markets and segments:
- High SOM with low growth may be a defend or harvest area.
- Low SOM with high growth and good margins may be a priority expansion area.
- Assess whether specific segments (e.g., younger demographics, certain industries) show disproportionate SOM gains or losses.
Performance review and forecasting
- Monitor SOM trends over time (e.g., quarter-on-quarter, year-on-year) to spot:
- Early signs of competitive threats.
- The impact of pricing changes, product launches, and distribution shifts.
- Use SOM as an input into forecasting models:
- Project future SOM based on historic response to marketing investment and category growth scenarios.
Common use cases include annual brand planning, category strategy reviews, investor communications, and evaluating the impact of major campaigns or product changes.
Comparison to similar approaches and metrics
| Metric | What it Measures | Basis | Primary Use Case |
|---|---|---|---|
| Share of Market (SOM) | Brand’s share of total category sales | Revenue or units | Competitive position and growth performance |
| Share of Voice (SOV) | Brand’s share of communication weight | Spend, impressions, GRPs | Media planning and competitive visibility |
| Share of Search | Brand’s share of category-related search interest | Search query volume | Early signal of interest and consideration |
| Penetration | Percentage of buyers who purchase the brand | Number of buyers | Brand reach within the buying population |
| Category Growth | Rate of total category expansion or contraction | Revenue or units over time | Market attractiveness and context for brand performance |
| Market Share by Channel | SOM broken out by distribution or media channel | Sales per channel | Channel strategy, retail and e-commerce optimization |
| Customer Share | Share of wallet within existing customers | Customer-level sales data | Cross-sell and upsell effectiveness |
| Brand Awareness | Proportion of audience aware of the brand | Survey metrics | Mental availability and brand salience |
SOM focuses on what the market actually bought, while SOV and awareness focus on what the market saw or remembers. Together, they form a link between investment, perception, and outcome.
Best practices
- Define the category precisely
Make sure the denominator (total category sales) matches your strategic frame:- Same product types or solutions.
- Same geography, channel, and time period.
- A realistic competitive set (neither too broad nor too narrow).
- Use consistent sources and methodology
SOM is most useful as a trend. To make comparisons meaningful:- Use the same data provider(s) over time where possible.
- Keep definitions (category, time horizon, currency, volume units) stable.
- Document any scope changes clearly when they occur.
- Break down SOM into useful cuts
Average SOM can hide important dynamics. Where data allows:- View SOM by key geographies, segments, and channels.
- Examine SOM in priority subcategories (e.g., premium vs. mass, core vs. new usage occasions).
- Pair SOM with leading indicators
Combine SOM with:- SOV and media metrics, to understand whether share of spending aligns with outcomes.
- Brand metrics (awareness, consideration, preference) to diagnose where the funnel is strong or weak.
- Distribution, pricing, and product metrics to understand structural drivers of share.
- Look at both level and trend
- High SOM with flat or declining trend may signal structural issues or stronger competitors emerging.
- Low SOM with positive trend can indicate momentum that marketing should accelerate.
- Abrupt SOM shifts usually warrant investigation into pricing changes, distribution loss/gain, competitor launches, or macro factors.
- Integrate SOM into decision-making, not just reporting
Use SOM as a trigger for actions:- Increase or reallocate marketing investment.
- Adjust channel focus or product mix.
- Revisit positioning or pricing strategies.
Future trends
- More granular, near real-time SOM data
With the growth of digital channels, point-of-sale systems, and marketplaces, SOM measurement is moving:- From quarterly or annual updates to monthly or even weekly views in some categories.
- Toward more granular breakdowns by micro-segment, context, or platform.
- Closer linkage between SOM and customer-level data
SOM will be combined more frequently with:- Customer acquisition, retention, and cohort analysis.
- Customer lifetime value and profitability metrics.
This will help distinguish between “cheap share” and “valuable share.”
- Category and ecosystem redefinition
As boundaries between categories blur (e.g., software and services, physical and digital products), SOM definitions will:- Expand to reflect solution-based categories.
- Be recalibrated when disruptors reshape how customers think about the space.
- AI-assisted share modeling
AI and advanced analytics will support:- Estimating SOM where data is incomplete or fragmented.
- Simulating the potential impact of different investment or pricing scenarios on future SOM.
- Linking SOM changes more clearly to specific marketing and commercial levers.
- Integration into unified performance dashboards
SOM will increasingly appear alongside SOV, share of search, brand health, and financial metrics in integrated marketing and commercial dashboards, giving leaders a more coherent view of performance across the funnel.
Related Terms
- Share of Voice (SOV)
- Share of Search
- Market Penetration
- Category Growth
- Market Segmentation
- Brand Awareness
- Customer Lifetime Value (CLV)
- Brand Equity
- Competitive Positioning
- Go-to-Market Strategy