Before launching a product or starting a new company, you need to answer a fundamental question: how many people could actually buy what you're selling? Answering that question is the core of market sizing. It’s the process of estimating the potential number of customers and the total potential revenue for your product or service.

Think of it like setting up a stall at a farmers market. You'd want to know how many people visit the market each weekend, how many of them are looking for the kind of produce you sell, and how many you can realistically serve before you run out of stock or they buy from a competitor. Without these estimates, you’d be flying blind—unsure how much to grow, what to charge, or if the market is even worth your time.

Market sizing is a critical first step in any business strategy. For a startup, a clear market size calculation can convince investors that the business has growth potential. For an established company, it helps justify the investment in a new product line. It sets the foundation for sales targets, marketing budgets, and overall business goals.

To get an accurate picture, it’s not enough to find one giant number for

These three layers help a business move from a broad, theoretical market down to a specific, actionable target.

The Total Addressable Market is the biggest possible slice of the pie. It represents the total demand for a product or service across all segments and all competitors. It’s the theoretical maximum revenue you could generate if you were the only provider and captured every single potential customer in the world.

For example, the TAM for cars would include every person and organization globally that could potentially buy a new vehicle. It's a huge, optimistic number that defines the upper limit of the market.

Of course, no company can serve the entire global market. The Serviceable Available Market is the portion of the TAM that your business can actually reach with its products, services, and sales channels. It's filtered by factors you can't or don't plan to address.

For our car company, the SAM might be limited by geography (only selling in North America), product type (only selling electric SUVs), or language (only providing customer support in English). SAM is a more realistic view of the market segment you are targeting.

Finally, we have the Serviceable Obtainable Market. This is the slice of the SAM that you can realistically capture in the short term, considering your competition, marketing efforts, and resources. It's your target.

Even within your reachable market (SAM), you won't win every customer. Some will choose competitors, others may not be ready to buy. Your SOM is your share of the available market. For the electric SUV company, the SOM would be the sales goal for the next year based on its production capacity, brand awareness, and the strength of its rivals.

Understanding these three levels is crucial. It gives businesses a framework for ambition (TAM), strategy (SAM), and execution (SOM), turning a vague goal into a concrete plan.

Now, let's test your understanding of these core concepts.

By breaking the market down this way, businesses can create more focused strategies and set achievable goals.