【V+觀點】市場規模不是數學題，是策略題

Cory Chiang
5月14日
讀畢需時 6 分鐘

The English translation of the article can be found after the Chinese version.

不論是創辦人在對創投 pitch，還是創投同仁準備投審會報告時，「市場規模」永遠是一道必答題。以我自己為例，看似簡單的 TAM、SAM、SOM 三段式架構，實際操作起來卻往往是費時、也最容易被挑戰的部分。

市場要怎麼切？公司到底可以吃到多少？既要有想像力，又不能脫離現實，一邊要 top-down 看產業趨勢，一邊又要 bottom-up 精算產品能吃下多少。這不只是「數學題」，更是一道「策略題」——你怎麼定義你自己要打的市場？

先釐清：什麼是 TAM / SAM / SOM？

TAM（Total Addressable Market）：理論上整個產業的最大市場規模，如果這世界完全運作在你的理想中，你可以吃下的市場。
SAM（Serviceable Available Market）：指的是你目前「有能力服務到」的市場範圍，也可以理解為你可接觸市場中「潛在客戶」的那一群。
SOM（Serviceable Obtainable Market）：在 SAM 裡，根據你目前的商業模式與資源，你「實際可以吃到的那一塊」。

我們以一間主打中小企業的人資管理 SaaS 新創為例，產品涵蓋請假、薪資、打卡、績效等功能，強調快速導入、免 IT 支援。

TAM：亞洲約有 3,000 萬家具備導入 HRM 系統潛力的企業，若每年平均支出 1 萬台幣，TAM 約為 3,000 億台幣。
SAM：目前僅聚焦台灣與新加坡、20–200 人規模企業，約 200 萬間，SAM 約為 200 億台幣。
SOM：假設可觸及 60%、轉化率 20%，SOM約 24 億台幣。

這樣看起來清楚有邏輯，但實務上卻經常出現錯用、誤解或過度簡化的狀況，許多 pitch deck 雖然寫出了 TAM / SAM / SOM，但一問之下，背後的估算方法其實站不住腳，常見的認知落差如下。

認知落差一：用錯方法計算 TAM / SAM / SOM

最常見的畫法錯誤有：

隨便抓產業報告或 Google 搜尋的產值總和當 TAM
把 TAM 等比例切下來當 SAM / SOM（如 TAM 是 100 億，SAM 就是 10 億，SOM 是 1 億）
沒有說明切分依據與驗證邏輯

正確的方式應該是：

先定義你的市場區塊、產品類型、使用場景與核心客群
根據可接觸的市場範圍定義 SAM（從行銷／銷售／地區／語言等條件收斂）
SOM 必須能對應目前的 go-to-market 策略與預算，最好有轉換率驗證、早期用戶數據或客戶回饋支撐

認知落差二：創辦人只做 top-down

許多創辦人習慣用 top-down 的方式來估市場規模：「這個產業一年產值 500 億美金，只要我們吃下 1%，就是 5 億美金。」這種「從大數字往下切」的邏輯，雖然看起來簡單直觀，卻容易高估可達市場、低估執行難度，真正關鍵的 go-to-market 細節、轉換效率、單位經濟模型，反而被模糊了。

而創投更想看到的是 bottom-up 的推估方式：你預計服務哪一類型的客戶？他們在哪裡？願意付多少錢？你透過什麼渠道接觸？每個階段的轉換率是多少？這樣的估算方式雖然比較花時間，卻更能反映出商業模式與市場策略的可行性。

理想的市場推估方式，是 top-down 和 bottom-up 兩種方法交叉驗證、互為印證。宏觀願景固然重要，但若無法細緻拆解落地策略與數據假設，就容易變成空泛的畫餅，而非可信的成長邏輯。

創投希望看到的是什麼？

市場夠聚焦：而不是想打所有人
進入方式可操作：搭配明確的 go-to-market 計畫
假設能被驗證：市場假設能拆成具體的數據模型，並開始驗證

真正吸引人的市場規模，不是數字，而是邏輯。TAM / SAM / SOM 不是用來畫得多大，而是看你有沒有策略、有沒有選擇、有沒有方法，從畫餅到落地，關鍵不在於總量，而在於你能不能夠用有限的資源，證明你能在某一個利基市場裡活得下來、長得出來。

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關於VENTURE⁺

熟悉SaaS領域，並從產業本質出發，除了提供必要的資金協助之外，更帶給新創公司最缺乏的企業夥伴與產業資源合作、實務的成長策略經驗，以及資本市場的專業規劃建議。希望以最佳共同創業夥伴（Best Co-founding Partner）的心態，在SaaS新創、創投與產業企業三者間，建立起長期新創資源整合的合作橋樑。

Market Sizing Isn’t a Math Problem — It’s a Strategy Test

Whether it’s a founder pitching to investors or a VC preparing for an investment committee meeting, “market size” is always a must-answer question. In my experience, while the TAM/SAM/SOM framework looks simple on the surface, it often ends up being one of the most time-consuming—and most heavily challenged—parts of any discussion.

How should you define your market? How much can your company realistically capture? You need to balance ambition with grounded logic—using top-down industry insights while bottom-up estimating how much your product can actually eat. This isn’t just a math exercise—it’s a strategic decision: how you define the market you’re aiming to win.

First, What Are TAM / SAM / SOM?

TAM (Total Addressable Market): The total size of the industry in your ideal world—if everything works out perfectly and your product dominates the market.
SAM (Serviceable Available Market): The portion of TAM that your product can realistically serve based on your business model and operational reach.
SOM (Serviceable Obtainable Market): The slice of SAM that you can realistically capture in the short term, based on your current resources and go-to-market strategy.

Let’s use an HRM SaaS company as an example. This startup targets small and mid-sized businesses with cloud-based HR software covering leave management, payroll, attendance, and performance tracking—designed for fast deployment and no IT staff required.

TAM: In Asia, there are roughly 30 million businesses with potential to adopt HRM software. Assuming an average annual spend of NT$10,000 per business, TAM is estimated at NT$300 billion.
SAM: The company currently focuses on Taiwan and Singapore, targeting businesses with 20–200 employees. There are around 2 million such businesses in these two markets, placing SAM at NT$20 billion.
SOM: If the team can reach 60% of this market and convert 20% of those, that translates to a SOM of roughly NT$2.4 billion.

While this framework looks clean and logical, in reality, founders often misapply, oversimplify, or miscalculate these numbers. Many pitch decks show TAM/SAM/SOM slides—but once challenged, the underlying assumptions often fall apart. The most common misalignments include:

Misalignment #1: Using the Wrong Method to Calculate TAM / SAM / SOM

Common mistakes we see:

Taking a generic market report or Google search figure as TAM
Cutting TAM by arbitrary percentages to produce SAM/SOM (e.g., TAM = $10B → SAM = $1B → SOM = $100M)
Failing to explain segmentation logic or validate assumptions

The right approach should be:

Clearly define your market segment, product scope, use cases, and target customers
Use marketing, sales, geography, and language filters to narrow SAM
Ensure SOM aligns with your actual go-to-market strategy and budget—ideally supported by conversion data, pilot users, or customer feedback

Misalignment #2: Relying Solely on Top-Down Thinking

Many founders rely on a top-down logic like:

“This industry is worth $50 billion per year. If we capture just 1%, that’s $500 million.”

It sounds straightforward, but it often overestimates the accessible market while underestimating execution challenges. Key elements like GTM strategy, conversion funnels, and unit economics often get glossed over.

What investors want to see is a bottom-up approach:

Who exactly are your target users?
Where are they?
How much are they willing to pay?
How will you reach them?
What are your expected conversion rates at each step?

This method takes more effort but provides a clearer picture of the viability of your business model and strategy.

In an ideal world, top-down and bottom-up analyses should cross-validate. The big vision gives direction, but without tactical clarity and numbers to back it up, it’s just wishful thinking—not a credible growth plan.

What Do VCs Actually Want to See?

A focused market: Not “we can serve everyone”
An executable entry strategy: Clear GTM plan that matches your team and resources
Testable assumptions: Market segmentation that can be translated into numbers and actually validated

The Most Convincing Market Size Isn’t About Big Numbers—It’s About Sharp Logic

TAM/SAM/SOM isn’t about drawing the biggest possible circles. It’s about whether you’ve made the right strategic choices. Whether you know where to start. Whether you have a method to win with limited resources. Whether you can prove you can survive—and scale—from a focused niche. From dream to traction, the key isn’t the total size of the pie, but your strategy to earn your first slice.

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About VENTURE⁺We specialize in the SaaS sector, approaching from an industry-first perspective. In addition to providing essential funding, we connect startups with the corporate partners and industry resources they need the most. We also share hands-on strategies for sustainable growth and offer professional advice on capital market planning.VENTURE⁺ aims to be the Best Co-founding Partner for SaaS startups—building a long-term, integrated bridge between startups, venture capital, and industry leaders.

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