Market Sizing in Saudi Arabia: Making TAM, SAM and SOM Useful
Make TAM, SAM and SOM operational definitions tied to a scope, time period, unit and visible assumptions—not figures detached from reachability.
Define the market before choosing the acronym
TAM, SAM or SOM has no useful value until you answer: what exactly are we counting as a market? Define the category or need, geography, customer type, time period and unit. Are you counting organisations, sites or users? Is the measure annual spending on a defined category, or potential revenue for a particular offer? Changing any definition can change an estimate materially, so state the scope beside every result instead of letting acronyms stand in for it.
TAM is commonly used for the total theoretical market under the chosen definition; SAM for the portion that fits a particular offer or service scope; and SOM for the portion a company could reasonably target or obtain under conditions of access, capability and competition. These are thinking layers, not findings in themselves, and their operational definitions depend on the decision. Do not equate theoretical opportunity with accessible share, or reachability with realised revenue or profit.
Choose the unit: customers or revenue? Spend or profit?
Choose a unit the team can interpret and validate. Estimating the number of potential customers answers a different question from estimating their spending value. Category spending may describe a total budget that a new product cannot capture. An assumed revenue figure requires additional assumptions about price, purchase and repeat behaviour; profit also depends on costs and economics. Do not multiply counts by average spend unless the source and scope of each input are known.
Create a scope card for each estimate:
| Scope field | What to record |
|---|---|
| Category or need | What product, service or spending is included, and what is excluded? |
| Geography | Which areas are covered, and what location differences or exclusions apply? |
| Customer | Unit of count—organisation, site, person, household or other—and eligibility rule. |
| Period | Year or horizon, and how change over time is handled. |
| Unit | Customer count, units, spending value or revenue; do not conflate them. |
| Decision use | Which decision will the figure inform, and what does it not prove? |
Compare a top-down estimate with a bottom-up one
A top-down estimate starts with a relevant aggregate source and narrows it using stated factors such as category, geography or customer eligibility. It can help test context and consistency, but an unsupported narrowing percentage creates false precision. Check the source’s definition, date and unit, and ask whether it actually matches the market you defined.
A bottom-up estimate starts with explainable units—for example, eligible accounts in scope multiplied by a stated purchase assumption, or a sum of observed spending where suitable data exists. It can make the estimate’s connection to an offer clearer, but it is vulnerable to missing accounts and assumptions about purchase rate, price and frequency. Do not hide these assumptions inside the arithmetic.
Use the approaches as independent estimates to compare, not as a way to select the number you prefer. If they differ, examine differences in definition, counting unit, source coverage or assumptions. Agreement does not automatically prove accuracy; both paths may rely on the same weak source or premise.
Record inputs, sources and confidence
| Input | Source or estimation approach | Confidence and why |
|---|---|---|
| Category and market definition | Documented internal definition or clear classification reviewed by decision owners. | Higher when agreed; lower when boundaries are ambiguous. |
| Number of eligible units | A source fitting the scope, or a documented count with known date and coverage. | Assess recency, completeness and alignment of definitions. |
| Spend or value per unit | Reviewable data or a stated assumption that still needs validation. | An average alone does not justify high confidence; test variation and fit. |
| Reachability or purchase | Evidence on channels, eligibility, operating capability and choice behaviour. | Depends on evidence quality; stated intent alone does not establish a purchase. |
| Company’s obtainable share | A scenario that makes competition, resources, time and constraints visible. | Conditional on assumptions, not a fact independent of them. |
Confidence can be described qualitatively—high, medium or low—with an explicit reason for each input, instead of one label implying that every part of the calculation is equally reliable. Show scenarios by varying sensitive assumptions and state what additional evidence is needed. Do not fill the template with unavailable numbers: record “unknown” and identify how to validate it.
Separate theoretical, serviceable and obtainable
TAM may be much broader than an offer can serve. SAM narrows the scope according to product fit, geography and route to market. SOM should account for what the company can realistically target over a defined horizon, given resources, channels, competition and operational constraints. Even that is not a promise of share or sales; it is an estimate conditional on visible assumptions.
**Educational hypothetical example with no market figures:** A company is considering a specialised service for organisations. It first defines the organisations with the relevant need, the geography and period, then describes theoretical TAM under that definition. It excludes from SAM units the product does not fit or the selected operating model cannot serve. For a SOM scenario, it examines reachable accounts, adoption feasibility, resources and alternatives. No figure is supplied here; the team would need to gather reliable inputs and show what remains unknown before making an investment decision.
Limits and biases
Published sources may be dated or use a different classification; an internal count may overstate coverage or miss units that are not visible. Combining incompatible sources can double-count the same units. Applying category spending to a company’s offer can imply that all of that spend is convertible. Share scenarios can also reflect internal ambition more than evidence of reach.
Separate customers from revenue, spending from profit, and theoretical market from the portion that can be reached. State the time horizon, source date and assumptions for every input. Where uncertainty matters, show scenarios rather than a single number. Market Opportunity Scan can organise opportunity questions, assumptions and evidence gaps; NOMAS 90-Day Blueprint can later help organise priorities into a plan, but it does not validate an estimate or guarantee a commercial outcome.
Practical summary
Write the market definition, unit and period before calculating. Compare a top-down approach with a bottom-up one, and explain disagreement rather than hiding it. Document each input’s source and confidence, then test sensitive assumptions through scenarios. Treat TAM, SAM and SOM as conditional analytical boundaries—not guaranteed sales or profit figures.
**Discuss your market opportunity with NOMAS.** Contact our team, call 0552641003 (+966552641003), or email sabah@wenomas.com.
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