RESULT OBTAINED
03 · TAM, SAM and SOM
TAM, SAM and SOM: size the opportunity without confusing the three
What must be established
A useful analysis leaves its controls visible.
- 01
Define the offer, buyer and unit before calculating.
- 02
Show every filter between total, serviceable and obtainable scope.
- 03
Treat SOM as a conditional estimate, not a sales promise.
Decision checkpoint
Make the next choice explicit.
DECISION SUPPORTED
Which opportunity is theoretical, serviceable and realistically obtainable?
DELIVERABLE TO RETAIN
Three aligned ranges with filters, assumptions and a review condition.
NEXT ITEM TO INVESTIGATE
Define the marketExplore →Set the decision boundary
Start from the decision: whether to investigate, enter or resource a defined offer. TAM describes the broad eligible universe; SAM applies the constraints that make the offer serviceable; SOM adds the conditions under which a share could be won in the selected horizon.
- Decision owner
- Scope and horizon
- Comparable alternatives
Make evidence and calculation inspectable
Every transition must retain its population, unit, source year and filter. A bottom-up count of reachable accounts can challenge a top-down market value; their gap is evidence to investigate, not a number to average away.
- Source and date
- Unit and calculation
- Known uncertainty
Keep a reopening rule
Reopen the sizing when eligibility, geography, channel access, capacity or the offer itself changes. The decision record should state which range would alter the investment and who checks the trigger.
- Material signal
- Decision effect
- Owner and review date
Application protocol
Turn the method into a reviewable decision record.
The page is complete only when another reviewer can reproduce the boundary, trace the evidence and understand what would change the conclusion.
Frame before measuring
Name the owner, decision, alternatives, unit, geography and horizon before collecting figures. This prevents a convenient source or familiar category from silently defining the problem.
- Decision and owner
- Comparable options
- Unit, boundary and horizon
Separate observation from judgement
Record every observation with source, date, method and unit. Keep transformation rules, scores and weights apart from the evidence so that disagreement can target the right layer.
- Observed evidence
- Calculation convention
- Assumption and confidence
Plan the reopening rule
State the signal, threshold, owner and review date that would reopen the choice. A robust conclusion is conditional and operational; it is not made permanent by a polished score.
- Material signal
- Decision threshold
- Owner and review date
Resources
Reuse the method and check its foundations.
- UK Government, The AQuA Book (opens in a new tab)Reference used to document assumptions, scope and the limits of market analysis. Useful for transparent assumptions and reproducible population filters.
- U.S. Census Bureau, Business Builder (opens in a new tab)Reference used to document assumptions, scope and the limits of market analysis. Useful for transparent assumptions and reproducible population filters.
01Explicit scope
Unit, horizon and boundaries are visible.
02Qualified evidence
Source, date, method and confidence are recorded.
03Sensitivity tested
Weights and assumptions that reverse the result are known.
04Review planned
Signal, threshold, date and owner are named.
RETURN TO THE DECISION SYSTEM
See the canonical definition of marketing strategy→