Market Size

Understanding Market Size: A Comprehensive Guide for Startups

Kurt GraverBusiness Start-up Advice, Business Success Formula, Marketing & Sales

As a startup founder, one of the most critical factors in determining the success of your venture is understanding the size of your target market. Market size refers to the potential demand for your product or service within a specific industry or niche. According to a study by CB Insights, startups fail due to misreading market demand, with 42% of failures attributed to this factor (CB Insights, 2019).

Assessing market size is crucial for several reasons. First, it helps you determine whether your offering has sufficient demand to sustain and grow your business. Second, it informs your go-to-market strategy, including pricing, distribution, and marketing decisions. Third, it is a key factor that investors consider when evaluating the potential of your startup.

In this comprehensive guide, we’ll dive deep into the concept of market size, exploring its significance, the different types of market sizing, and the practical steps you can take to calculate and interpret market size for your startup. By the end of this guide, you’ll have a solid understanding of how to assess market demand and make informed decisions to drive your startup’s growth and success.

Why Market Size Matters for Startups

Market size is a critical consideration for startups for several reasons:

1. Assessing Business Viability

Understanding the size of your target market helps you determine whether your business idea is viable and sustainable in the long run. If the market is too small, there may not be enough potential customers to generate sufficient revenue and growth. On the other hand, if the market is too large, it may be challenging to differentiate your offering and capture market share.

According to a report by the Small Business Administration, the optimal market size for a startup is large enough to provide ample growth opportunities but not so large that it attracts too many competitors (SBA, 2021).

2. Informing Go-to-Market Strategy

Market size insights can help you make informed decisions about your go-to-market strategy, including:

  • Pricing: Understanding the size and value of your target market can help you determine the optimal price point for your product or service based on customer willingness to pay and competitive benchmarks.
  • Distribution: Market size can inform your distribution strategy, helping you prioritize the channels and geographies that offer the greatest growth potential.
  • Marketing: Insights into market size and segmentation can guide your marketing efforts, allowing you to tailor your messaging and targeting to the most promising customer segments.

3. Attracting Investors

Investors pay close attention to market size when evaluating startups, which is a key indicator of growth potential and scalability. According to a survey by the National Venture Capital Association, market size is the second most important factor investors consider when making funding decisions after the strength of the management team (NVCA, 2020).

To attract investors, startups must demonstrate a compelling market opportunity backed by credible data and analysis. This includes estimating the overall market size and identifying the specific segments and niches where the startup can establish a competitive advantage.

4. Setting Realistic Growth Targets

Understanding market size helps startups set realistic growth targets and milestones. By knowing the total addressable market (TAM), startups can estimate their potential market share and revenue potential over time. This information is critical for creating financial projections, allocating resources, and measuring progress.

Without a clear understanding of the market size, startups risk setting overly ambitious or conservative targets, which can lead to misaligned expectations and suboptimal decision-making.

Types of Market Sizing

There are several types of market sizing that startups should be familiar with:

1. Total Addressable Market (TAM)

TAM refers to the total market demand for a product or service, assuming 100% market share. It represents the maximum potential revenue a company could generate if it captured the entire market.

To calculate TAM, you can use a top-down or bottom-up approach:

  • Top-down: Start with the total market size for your industry or niche, then narrow it down based on your specific target segments and geographies.
  • Bottom-up: Start with your target customer base, estimate their average annual spending on your product or service, and multiply by the total number of potential customers.

While TAM is a useful starting point, it’s important to remember that it represents a theoretical maximum and may not be achievable in practice.

2. Serviceable Available Market (SAM)

SAM refers to the portion of the TAM currently served by existing products or services. It represents the market size your startup can realistically target and compete in.

To calculate SAM, start with your TAM and apply filters based on factors such as:

  • Geographic availability: The regions or countries where your product or service will be available.
  • Customer segmentation: The specific customer segments or verticals that you will target.
  • Product or service fit: The market portion that aligns with your specific value proposition and features.

SAM provides a more realistic estimate of your potential market size and helps you focus your go-to-market efforts on the most promising opportunities.

3. Serviceable Obtainable Market (SOM)

SOM refers to the portion of the SAM that your startup can realistically capture over a specific period, given your current resources, capabilities, and competition.

To calculate SOM, start with your SAM and apply additional filters based on factors such as:

  • Market share is the percentage of the market that you can realistically capture based on your competitive position and growth rate.
  • Sales and marketing capacity is the portion of the market that you can effectively reach and convert, given your current sales and marketing resources.
  • Product or service limitations: Any constraints or limitations in your offering that may limit your ability to serve the entire SAM.

SOM provides a realistic and actionable growth target for your startup and helps you align your resources and strategies accordingly.

How to Calculate Market Size

Now that we’ve covered the different types of market sizing let’s explore the practical steps you can take to calculate the market size for your startup.

Step 1: Define Your Target Market

The first step in calculating market size is clearly defining your target market. This includes specifying the following elements:

  • Industry or niche: The broad or specific niche your product or service belongs to.
  • Customer segments are the specific customer groups or verticals you will target based on demographics, psychographics, and behaviour.
  • Geographic scope: The regions, countries, or cities where you will offer your product or service.
  • Product or service category: The specific type of product or service that you offer and how it is differentiated from competitors.

By clearly defining your target market, you can ensure that your market sizing efforts are focused and relevant to your startup’s unique value proposition.

Step 2: Gather Market Data

The next step is to gather credible data on your target market size. There are several sources you can use, including:

  • Industry reports and market research: Look for reputable market research studies and analyst reports that provide estimates of market size and growth for your specific industry or niche.
  • Government data: Government agencies such as the U.S. Census Bureau, Bureau of Labor Statistics, and International Trade Administration provide valuable data on industries, demographics, and economic trends.
  • Company financial reports: If you have publicly traded competitors, their financial reports and investor presentations may provide insights into market size and share.
  • Surveys and primary research: Consider conducting your own surveys or interviews with potential customers to gather data on their needs, preferences, and willingness to pay.

When gathering market data, it’s important to assess the credibility and reliability of each source. Look for data that is recent, specific to your target market, and based on sound methodology.

Step 3: Calculate TAM

Once you have gathered market data, you can calculate your TAM using either a top-down or bottom-up approach.

For a top-down approach:

  1. Start with the total market size for your industry or niche.
  2. Apply filters based on your target customer segments and geographic scope.
  3. Multiply the resulting number by the average revenue per customer or unit to arrive at your TAM.

For example, let’s say you are starting a subscription-based online fitness platform. Your target market is health-conscious millennials in the United States. According to industry reports, the total U.S. fitness industry is worth $35 billion, and millennials make up 30% of the market. The average revenue per user for online fitness subscriptions is $150 per year.

Using a top-down approach, your TAM would be:
$35 billion x 30% x $150 = $1.575 billion

For a bottom-up approach:

  1. Estimate the total number of potential customers in your target market.
  2. Multiply by the average revenue per customer or unit to arrive at your TAM.

Using the same online fitness platform example, let’s say there are 40 million health-conscious millennials in the United States. Using a bottom-up approach, your TAM would be:
40 million x $150 = $6 billion

As you can see, top-down and bottom-up approaches can yield different results. It’s important to use multiple methods and data sources to triangulate and validate your market size estimates.

Step 4: Calculate SAM and SOM

Once you have calculated your TAM, you can further refine your market size estimates by calculating your SAM and SOM.

To calculate SAM:

  1. Start with your TAM.
  2. Apply filters based on factors such as geographic availability, customer segmentation, and product or service fit.
  3. Multiply the resulting number by the average revenue per customer or unit.

For example, let’s say that based on your current resources and capabilities, you can only realistically serve 50% of the U.S. millennial fitness market. Your SAM would be:
$1.575 billion x 50% = $787.5 million

To calculate SOM:

  1. Start with your SAM.
  2. Estimate your realistic market share based on factors such as your competitive position, sales and marketing capacity, and product or service limitations.
  3. Multiply the resulting number by the average revenue per customer or unit.

Continuing with the online fitness platform example, let’s say that based on your current stage and resources, you believe you can capture 5% of the SAM within the next 3 years. Your SOM would be:
$787.5 million x 5% = $39.4 million

Interpreting and Applying Market Size Insights

Calculating market size is just the first step. To truly leverage these insights for your startup’s growth and success, you need to interpret and apply them effectively.

Here are some key ways to use market size insights:

1. Assess Market Opportunity

Use your TAM, SAM, and SOM estimates to assess your target market’s overall attractiveness and potential. Consider factors such as:

  • Market growth rate: Is the market growing, stable, or declining? A growing market generally offers more opportunities for new entrants.
  • Competitive landscape: How many competitors are there, and what is their market share? A highly fragmented market may be easier to penetrate than one dominated by a few large players.
  • Customer needs and preferences: Are there unmet needs or underserved segments that your startup can address? A market with strong customer demand and willingness to pay is more attractive than one with limited interest.

By assessing the market opportunity through the lens of market size, you can make informed decisions about whether to enter a market, how to position your offering, and where to focus your resources.

2. Set Realistic Growth Targets

Use your SAM and SOM estimates to set realistic growth targets and milestones for your startup. Consider factors such as:

  • Market share: Given your current resources and competitive position, what percentage of the market can you realistically capture over time?
  • Revenue potential: Based on your average revenue per customer or unit, how much revenue can you generate at different levels of market penetration?
  • Profitability: What level of market share and revenue do you need to achieve profitability, given your cost structure and pricing strategy?

By setting realistic growth targets based on market size insights, you can align your team, investors, and stakeholders around a common vision and roadmap for success.

3. Inform Go-to-Market Strategy

Use your market size insights to inform your go-to-market strategy, including:

  • Pricing: Based on your target market size and willingness to pay, what is the optimal price point for your product or service? Consider factors such as cost structure, competitive benchmarks, and customer value perception.
  • Distribution: Based on your target customer segments and geographic scope, what are the most effective channels and partnerships for reaching and serving your market? Consider factors such as cost, scalability, and alignment with customer preferences.
  • Marketing: Based on your target customer segments and market size, what are the most effective marketing tactics and messages for building awareness, generating leads, and driving conversions? Consider factors such as customer pain points, decision-making process, and media consumption habits.

By aligning your go-to-market strategy with your market size insights, you can optimize your resources and efforts for maximum impact and efficiency.


Understanding market size is a critical foundation for startup success. By accurately assessing the size and potential of your target market, you can make informed decisions about your business model, go-to-market strategy, and growth targets. Market size insights can also help you attract investors, partners, and customers by demonstrating the viability and scalability of your venture.

However, calculating market size is not a one-time exercise. As your startup grows and evolves, it’s important to continuously monitor and reassess your market size assumptions based on new data, insights, and feedback. By staying attuned to market trends and customer needs, you can adapt your strategy and offerings to capitalize on new opportunities and maintain a competitive edge.

Ultimately, the key to leveraging market size insights for startup success is to use them as a starting point for validation, experimentation, and iteration. By combining market size analysis with customer discovery, product-market fit testing, and agile execution, you can create a startup that not only addresses a large and growing market opportunity but also delivers exceptional value to your target customers.

As you embark on your startup journey, remember that understanding market size is just one piece of the puzzle. Equally important are team quality, product innovation, customer experience, and operational excellence. By taking a holistic and data-driven approach to startup growth, you can navigate your market’s challenges and opportunities with confidence and resilience.