Most people first encounter TAM, SAM and SOM in the startup world—usually while pitching investors.

It's the classic market sizing slide:

• TAM – the Total Addressable Market
• SAM – the Serviceable Available Market
• SOM – the Serviceable Obtainable Market

It’s designed to show ambition, realism, and traction: How big is the opportunity? What can we actually serve? What are we going to target first?

But here’s the thing: this model isn’t just useful for new ventures. It’s one of the most underused and undervalued tools for internal strategy and operational decision-making.

In our work with large organisations—from public sector reform to corporate transformation—we’ve started teaching leaders how to apply TAM/SAM/SOM inside the enterprise.

Because whether you’re rolling out a new policy, digitising a service, or shifting behaviour across a workforce, you face the same question:

Is this problem big enough to matter?

Why do internal teams get scale so wrong? 

Inside complex systems, it’s surprisingly easy to misjudge problem size. We see it all of the time. Teams over-invest in issues that affect only a small user subset. Transformation programs try to “go big” before they’ve earned relevance. Business cases get built without clarity on who the solution actually reaches.

That’s where TAM/SAM/SOM helps. It grounds strategy in logic—not just enthusiasm. It helps teams distinguish the interesting from the important.

A quick refresher: TAM, SAM and SOM

For those unfamiliar or rusty, here’s how the model works:

It’s a cascading filter—from total relevance to realistic delivery.

And yes, even in internal change, you have a SOM. Because in every organisation, there are limits: technology, budget, policy, access, timing, capability.

A real-world example: internal payroll reform

One of our longstanding partners was revamping their payroll process. Leadership saw frustration across the organisation—manual approvals, delays, and confusion.

Here’s how we helped them apply the TAM/SAM/SOM model:

• TAM: All 18,000 employees who receive payslips
  
  
• SAM: The 4,200 employees who use the legacy system
  
  
• SOM: The 80 payroll officers and HR managers who handle the process directly.

It quickly reframed the strategy. Rather than trying to launch a universal fix, the team focused on the core operational group first. They could improve experience, gather feedback, and build internal credibility—then scale.

This wasn't a go-to-market strategy. It was a go-to-impact strategy.

Why this matters for internal innovation

There’s a reason Lean Startup principles and market frameworks are being adopted in government, infrastructure, and professional services: because clarity beats complexity.

In large systems, it’s easy to chase solutions without sizing the problem. But as Clayton Christensen reminded us, sustainable innovation starts with understanding where value lies—and who it's for.

When teams use TAM/SAM/SOM internally, we’ve seen (i) more focused pilots, (ii) faster stakeholder buy-in, (iii) fewer abandoned initiatives and (iv) learer prioritisation in budgeting rounds. 

Tips for using the framework inside your organisation

• Start with users, not spreadsheets: Estimating TAM/SAM/SOM doesn’t require perfect data. But it does require understanding who’s experiencing the problem, who’s reachable, and who’s ready.
  
  
• Make the constraints explicit: Don’t assume you can scale instantly. Factor in system access, behaviour change readiness, and cultural resistance.
  
  
• Use it to stage your rollout: Your SOM is your early traction zone. It’s where you learn, de-risk, and gather wins. Treat it like a live testbed.
  
  
• Return to it: TAM/SAM/SOM isn’t just a one-time scoping exercise. Revisit it as conditions shift. Your SOM today may be your SAM tomorrow.

Final thought: not everything is worth scaling

There are plenty of good ideas inside organisations that never go anywhere—not because they weren’t clever, but because they didn’t matter enough.

TAM/SAM/SOM helps you answer a powerful question:

Is this worth solving, at this scale, at this time?

It’s not just a startup pitch tool. It’s a strategic lens. One that every transformation team should have in their kit.