Size your total, serviceable and obtainable market, top-down from a market figure or bottom-up from real customers. Your numbers, the working shown, no sign-up.
TAM is the total yearly spend on what you sell, SAM is the part of it you can actually reach and serve, and SOM is the share of SAM you can realistically win. SOM in Year 5 = TAM today × (1 + yearly growth)⁵ × serviceable share × obtainable share. For example, a $500M market growing 8% a year, with 20% serviceable and 3% obtainable, gives a Year-5 SOM of about $4.4M.
You could realistically capture about $4.41M a year by Year 5, if your shares hold.
The Product Strategist researches your real market with cited sources, builds pessimistic, realistic and optimistic cases, and gives you a live market model you can download to Excel.
The total yearly spend on the problem you solve, by everyone who has it. It tells you whether the opportunity is big enough to matter, not how much of it you will get.
The slice of TAM your product can actually reach: the right customers, in the regions and channels you sell through, at your price. It is usually much smaller than TAM, and that is fine.
The share of SAM you can realistically win in the first few years, given competitors and your ability to sell. It is the number closest to your future revenue, which is why it deserves the most evidence.
A new product takes years to reach its share. Growing TAM to Year 5 before taking the two shares gives the obtainable market you are actually building toward. For the year-by-year path to it, the development cost and hardware cost calculators cover what it takes to get there.