TAM, SAM, SOM market sizing with top-down and bottom-up methods. Use when estimating addressable market, validating opportunity size, sizing new segments, or preparing investor pitch materials.

Reference medium

Primary Agent: product-strategist

Market Sizing

TAM/SAM/SOM framework for estimating addressable market and validating opportunity size.

Definitions

Metric	Definition	Question It Answers
TAM	Total Addressable Market — everyone who could possibly buy	"What's the theoretical ceiling?"
SAM	Serviceable Addressable Market — segment you can actually reach	"What can we realistically target?"
SOM	Serviceable Obtainable Market — realistic share in 3 years	"What will we actually capture?"

+-------------------------------------------------------+
|                         TAM                            |
|  +---------------------------------------------------+ |
|  |                      SAM                           | |
|  |  +-----------------------------------------------+| |
|  |  |                   SOM                          || |
|  |  +-----------------------------------------------+| |
|  +---------------------------------------------------+ |
+-------------------------------------------------------+

When to Use Top-Down vs. Bottom-Up

Method	Use When	Risk
Top-Down	Industry reports exist; investor pitch; quick estimate	Overestimates SOM
Bottom-Up	Sales capacity known; pricing validated; more credible	More work; requires assumptions
Both (recommended)	High-stakes decisions; fundraising; board decks	Cross-validate to build confidence

Always cross-validate both methods and reconcile within 20%. If they diverge by more than that, revisit your assumptions.

Quick Formulas

Top-Down
  TAM = (# potential customers) × (annual value per customer)
  SAM = TAM × (% your solution can address)
  SOM = SAM × (realistic market share % in 3 years)

Bottom-Up
  SOM = (# customers you can acquire) × (average deal size)
  SAM = SOM / (your expected market share %)
  TAM = SAM / (your segment as % of total market)

Example: AI Code Review Tool

## Market Sizing: AI Code Review Tool

### Top-Down

TAM
- Global developers: 28M
- Using code review tools: 60% → 16.8M
- Average annual spend: $300/developer
- TAM = $5.04B

SAM
- Enterprise only (>500 employees): 8M developers
- Willing to pay premium: 40% → 3.2M
- SAM = $960M

SOM
- Sales capacity supports ~$15M ARR (Year 3)
- Realistic market share: 2%
- Unconstrained SOM = $960M × 2% = $19.2M
- Constrained SOM = min($19.2M, $15M) = $15M

### Bottom-Up
- Target accounts Year 1: 50 enterprise deals
- Average ACV: $100K
- Year 1 ARR: $5M
- Year 3 (3× growth): $15M ARR → SOM = $15M

### Reconciled SOM: $15M (confirmed by both methods)

SOM Constraint Model

Do not report an unconstrained SOM. Always apply real-world limits:

SOM constraints:
  Sales capacity:       supports $15M ARR max
  Competitive pressure: 5 strong incumbents → −20% market share
  Go-to-market reach:   70% of SAM reachable with current channels

Conservative SOM = min(
  SAM × target_share%,
  sales_capacity_ceiling,
  SAM × gtm_reach% × target_share%
)

Confidence Levels

Confidence	Evidence Required
HIGH	Multiple corroborating sources, data < 2 years old
MEDIUM	Single authoritative source, 1-2 years old
LOW	Extrapolated, heavy assumptions, data > 2 years old

Always label each number with its confidence level in deliverables.

Common Mistakes

Mistake	Correction
TAM = "everyone on earth"	Define a specific, bounded customer segment
SOM = 10% of a billion-dollar market	Apply actual sales capacity and GTM constraints
Single method only	Cross-validate top-down and bottom-up
Old data	Use sources < 2 years old; flag if older
Ignoring competition	SOM must account for incumbents' share

References

TAM/SAM/SOM Rules — Calculation methods, SOM constraint model, cross-referencing
TAM/SAM/SOM Guide — Detailed guide with data source recommendations

ork:competitive-analysis — Understand competitive dynamics that constrain SOM
ork:business-case — Build financial justification once opportunity is sized
ork:product-frameworks — Full product strategy toolkit

Version: 1.0.0

Rules (1)

Size markets accurately using top-down and bottom-up approaches with realistic SOM constraints — HIGH

TAM/SAM/SOM Market Sizing

Market sizing from total opportunity to achievable share.

Framework Overview

+-------------------------------------------------------+
|                         TAM                            |
|        Total Addressable Market                        |
|     (Everyone who could possibly buy)                  |
|  +---------------------------------------------------+|
|  |                      SAM                           ||
|  |       Serviceable Addressable Market               ||
|  |    (Segment you can actually reach)                ||
|  |  +-----------------------------------------------+||
|  |  |                   SOM                          |||
|  |  |     Serviceable Obtainable Market              |||
|  |  |   (Realistic share you can capture)            |||
|  |  +-----------------------------------------------+||
|  +---------------------------------------------------+|
+-------------------------------------------------------+

Metric	Definition	Example
TAM	Total market demand globally	All project management software: $10B
SAM	Your target segment	Enterprise PM software in North America: $3B
SOM	What you can realistically capture	First 3 years with current resources: $50M

Calculation Methods

Top-Down Approach

TAM = (# of potential customers) x (annual value per customer)
SAM = TAM x (% addressable by your solution)
SOM = SAM x (realistic market share %)

Bottom-Up Approach

SOM = (# of customers you can acquire) x (average deal size)
SAM = SOM / (your expected market share %)
TAM = SAM / (segment % of total market)

Example Analysis

## Market Sizing: AI Code Review Tool

### TAM (Total Addressable Market)
- Global developers: 28 million
- % using code review tools: 60%
- Addressable developers: 16.8 million
- Average annual spend: $300/developer
- **TAM = $5.04 billion**

### SAM (Serviceable Addressable Market)
- Focus: Enterprise (>500 employees)
- Enterprise developers: 8 million (48% of addressable)
- Willing to pay premium: 40%
- Target developers: 3.2 million
- **SAM = $960 million**

### SOM (Serviceable Obtainable Market)
- Year 1-3 realistic market share: 2%
- **SOM = $19.2 million**

Cross-Referencing Methods

Always use both methods and reconcile:

Method	TAM	Notes
Top-Down	$4.86B	Based on industry reports
Bottom-Up	$5.0B	Based on enterprise segments
Reconciled	$4.9B	Average, validated range

SOM Constraints

SAM: $470M

Constraints:
- Market share goal (3 years): 3%
- Competitive pressure: -20%
- Sales capacity: supports $15M ARR
- Go-to-market reach: 70%

Conservative SOM: min($470M x 3%, $15M, $470M x 70% x 3%)
= min($14.1M, $15M, $9.87M)
= $10M (3-year target)

Confidence Levels

Confidence	Evidence
HIGH	Multiple corroborating sources, recent data
MEDIUM	Single authoritative source, 1-2 years old
LOW	Extrapolated, assumptions, old data

Common Mistakes

Mistake	Correction
TAM = "everyone"	Define specific customer segment
Ignoring competition	SOM must account for competitors
Old data	Use most recent (<2 years)
Single method	Cross-validate top-down and bottom-up
Confusing TAM/SAM	TAM is total, SAM is your reach

Incorrect — Unrealistic SOM without constraints:

TAM: $10B
SAM (our segment): $3B
SOM (10% market share): $300M

This is achievable in 3 years!

Correct — SOM constrained by realistic factors:

SAM: $3B

Constraints:
- Sales capacity: supports $15M ARR max
- Competitive pressure: 5 strong incumbents
- Realistic market share (Year 3): 0.5%

Conservative SOM: min($3B × 0.5%, $15M) = $15M

References (1)

Tam Sam Som Guide

TAM/SAM/SOM Market Sizing Guide

Comprehensive guide for market size estimation.

Definitions

TAM (Total Addressable Market)
└── "If we had 100% of the entire market"
└── The total market demand for a product/service

SAM (Serviceable Addressable Market)
└── "Segment we can actually reach"
└── TAM filtered by geography, segment, channel

SOM (Serviceable Obtainable Market)
└── "Realistic capture in 3 years"
└── SAM filtered by competition, capacity, go-to-market

Visual Hierarchy

┌─────────────────────────────────────────────────┐
│                    TAM                           │
│                 $10 Billion                      │
│  ┌─────────────────────────────────────────┐    │
│  │                SAM                       │    │
│  │             $500 Million                 │    │
│  │  ┌────────────────────────────────────┐ │    │
│  │  │              SOM                    │ │    │
│  │  │           $10 Million               │ │    │
│  │  └────────────────────────────────────┘ │    │
│  └─────────────────────────────────────────┘    │
└─────────────────────────────────────────────────┘

TAM Calculation Methods

Top-Down Approach

Start with industry reports and filter down.

Example: AI Developer Tools
1. Global software developer population: 27M (Statista 2026)
2. Developers using AI tools: 60% = 16.2M
3. Average spend on AI tools: $300/year
4. TAM = 16.2M × $300 = $4.86B

Bottom-Up Approach

Start with unit economics and scale up.

Example: AI Developer Tools
1. Target customer: Enterprise dev team (10+ devs)
2. Estimated teams globally: 500,000
3. Average contract value: $10,000/year
4. TAM = 500,000 × $10,000 = $5B

Cross-Reference

Always use both methods and reconcile:

Method	TAM	Notes
Top-Down	$4.86B	Based on Statista data
Bottom-Up	$5.0B	Based on enterprise segments
Reconciled	$4.9B	Average, validated range

SAM Calculation

Filter TAM by your actual reach:

Example: AI Developer Tools (US/EU focus)
TAM: $4.9B

Filters:
- Geography (US/EU only): 40% → $1.96B
- Segment (Enterprise only): 30% → $588M
- Use case (Python/TS devs): 80% → $470M

SAM: $470M

SOM Calculation

What you can realistically capture:

Example: AI Developer Tools
SAM: $470M

Constraints:
- Market share goal (3 years): 3%
- Competitive pressure: -20%
- Sales capacity: supports $15M ARR
- Go-to-market reach: 70%

Conservative SOM: min($470M × 3%, $15M, $470M × 70% × 3%)
= min($14.1M, $15M, $9.87M)
= $9.87M → Round to $10M

SOM: $10M (3-year target)

Data Sources

Primary Sources (Higher Confidence)

Gartner, Forrester, IDC reports
Company financials (public competitors)
Industry associations
Government statistics

Secondary Sources (Lower Confidence)

Press releases
Expert interviews
Survey data
LinkedIn data (company sizes)

Confidence Levels

Confidence	Evidence
HIGH	Multiple corroborating sources, recent data
MEDIUM	Single authoritative source, 1-2 years old
LOW	Extrapolated, assumptions, old data

Common Mistakes

Mistake	Correction
TAM = "everyone"	Define specific customer segment
Ignoring competition	SOM must account for competitors
Old data	Use most recent (<2 years)
Single method	Cross-validate top-down and bottom-up
Confusing TAM/SAM	TAM is total, SAM is your reach

Market Sizing

On this page