Why most market sizing is theater
The usual sequence runs like this. A number is needed for a board deck or an investor conversation. Someone finds an analyst report, applies a percentage, and produces a figure large enough to be encouraging. It goes into the deck. Nobody revisits it.
The cost is not the wasted afternoon. It is that budget allocation, hiring plans and go-to-market strategy get built on a denominator nobody believes. When results disappoint, the strategy is questioned rather than the arithmetic underneath it.
A defensible market size does two things. It supports decisions about where to invest, and it survives a hostile question from someone who has seen a lot of these.
TAM, SAM and SOM, defined properly
Total Addressable Market is everyone who could conceivably buy this category. Serviceable Addressable Market is the portion you can reach given your product, geography, segment focus and channel. Serviceable Obtainable Market is what you can realistically win in a defined period given your competition and capacity.
The common error is quoting TAM when SOM is the relevant number. TAM answers whether the category is worth entering. SOM answers what next year looks like. Presenting a large TAM in a conversation that requires SOM signals either confusion or evasion, and experienced investors read it as the latter.
A worked example clarifies. If there are 12,000 mid-market manufacturers in your geography, 4,000 have the operational complexity your product addresses, and you can credibly reach 15 percent through your current channel within three years at an average contract value of $40,000, your SOM is roughly $24 million. That number invites scrutiny of each assumption, which is precisely what makes it useful.
Top-down versus bottom-up
Top-down starts with a published market figure and narrows by segment. Fast, easy to produce, and only as good as the source definition, which rarely matches your actual market.
Bottom-up starts with account counts and unit economics and builds upward. Slower, more defensible, and it forces you to articulate assumptions explicitly.
Do both. Where they converge, confidence is reasonable. Where they diverge sharply, one of your assumptions is wrong and finding out which is more valuable than the number itself.
What primary research adds
Analyst reports describe a market as it appeared eighteen months ago, defined by categories the analyst chose rather than categories your buyers recognize.
Buyer interviews tell you what is happening now. More importantly, they tell you which budget line actually pays for you. This matters enormously and is almost never in a published report. A product that comes from the IT budget competes with different alternatives, at a different price ceiling, on a different approval timeline than the same product funded from an operations budget.
Twelve to twenty interviews within a defined segment usually reaches saturation.
Sizing a market that does not exist yet
Category creation makes conventional sizing impossible, because the category has no published figures and buyers cannot name a budget for something they do not know exists.
Three approaches help. Proxy markets, sizing the adjacent category buyers currently use to solve the problem badly. Budget displacement, identifying what spend you would replace. Problem prevalence, sizing the number of organizations experiencing the problem and estimating the proportion likely to act.
Present ranges rather than points, and state the uncertainty explicitly. A clearly caveated range is more credible than false precision.
Presenting to a board
Show the number, the method, and the assumptions table. The assumptions table is what makes it auditable and what separates analysis from assertion.
Expect three questions: how did you define the market, what happens if the penetration assumption is halved, and what is the competitive share assumption. Prepare all three.
Download the sizing template, or talk to us about primary market research.
Common questions
How many buyer interviews do we need for a defensible size?
Twelve to twenty in a defined segment usually reaches saturation. Beyond thirty you are mostly confirming what you already heard.
Can we use analyst reports instead?
As a triangulation input, yes. As the sole basis, no — they are lagging, broadly defined, and rarely match your actual serviceable market.
What is a realistic SOM for an early-stage company?
Usually a low single-digit percentage of SAM within three years. Anything higher needs an explicit explanation of why you will take share that fast.
How often should we resize?
Annually, or whenever you enter a new segment or the competitive set shifts materially.
