Seeking Clarity on TAM, SAM, SOM for Pre-Seed Pitch Decks

Hi everyone,

I’m currently working on my pre-seed pitch deck and am grappling with whether or not to include TAM, SAM, and SOM estimates. While I understand these are often considered essential in investor decks, I’d love to better understand their relevance, especially at this early stage.

Here are some specific questions I’m struggling with:

Why are TAM, SAM, and SOM numbers necessary for a pre-seed pitch?

Are investors primarily looking at these to gauge ambition, feasibility, or something else? Are there viable alternatives?

If these figures are difficult to estimate at such an early stage, are there other metrics or narratives that can work instead? How can I calculate and defend these numbers effectively?

What are realistic approaches to estimating these markets, especially in a domain that involves fragmented or emerging markets? How can I ensure these numbers hold up to scrutiny without overpromising? Any tips, resources, or anecdotes from your own experiences would be hugely helpful. I’d also love to hear from founders who opted not to include these numbers and how that played out.

Thanks in advance!