TAM/SAM/SOM calculator
Most TAM numbers come from an analyst report that sizes a category nobody on your team would recognize, then take 1% of it. That number cannot be checked and cannot be planned against. This calculator builds TAM from account counts by segment times a realistic ACV, narrows it to what you can actually serve, and caps SOM at what your team can physically close.
- Category:
- Territory & Quota
- Formats:
- CSV + web view
- Sections:
- 7
- Updated:
What you get
- A segment table that builds TAM from account count x ACV, not from a top-down percentage
- SAM filters (region, compatibility, segment served) applied as explicit percentages you can defend
- A SOM calculation based on achievable share, checked against rep capacity
- A worked three-segment example with every total shown
- A sources log so the account counts can be rebuilt next year
Who it's for
- RevOps and strategy leads preparing market sizing for a board or plan
- Founders and sales leaders replacing analyst-report TAM with real counts
- Finance partners checking that growth targets fit the market
What's inside
- 1
Model settings
5 fields to complete
- 2
TAM by segment
5 columns, 4 worked example rows
- 3
SAM by segment
6 columns, 4 worked example rows
- 4
SOM and capacity check
8 columns, 3 worked example rows
- 5
How the example adds up
Guidance notes
- 6
Sources log
5 columns, 3 worked example rows
- 7
Before you present the numbers
7-point checklist
Preview of section 1
Model settings
- Product or line being sized
- e.g. Core platform
- SOM horizon
- e.g. 3 years
- ACV source
- e.g. Median first-year ACV, closed-won, last 8 quarters
The preview shows part of section 1. The full template has all 7 sections (6 not previewed here), with blank rows ready to fill in. Download the full template
How to use it
- 1
Count accounts, do not estimate them
Pull account counts per segment from a firmographic database or your enrichment tool, using the same size bands as your territories. A count you can re-pull is worth more than a precise-looking number from a report.
- 2
Use ACV you actually achieve
Use median first-year ACV from closed-won deals in each segment, not list price at full deployment. If a segment has no closed-won history, label the ACV as an assumption and keep it conservative.
- 3
Make every SAM filter a separate line
Region, required integrations, language, and minimum company size each remove accounts. Write each as its own percentage with a source so anyone can challenge a specific filter instead of the whole number.
- 4
Cap SOM with capacity
Share-based SOM is only credible if your team can close that many deals in the horizon. Multiply reps x deals per rep per year x years and compare. If SOM exceeds capacity, capacity wins.
Frequently asked questions
How do you calculate TAM bottom-up?
Count the accounts in each segment that could use your product and multiply by a realistic ACV for that segment. Sum across segments. It is more defensible than a top-down percentage because every input can be checked.
What is the difference between TAM, SAM, and SOM?
TAM is every account that could use the product. SAM is the part you can actually sell to today, given your regions, integrations, and motions. SOM is the part you can realistically win in a set horizon, given share and team capacity.
What ACV should a TAM calculation use?
Median first-year ACV from closed-won deals in each segment. Full-deployment list price inflates TAM and makes SOM look easier to reach than it is.
How do you sanity-check SOM?
Compare the number of deals SOM implies with how many deals your AEs can close in the horizon. If SOM needs more deals than capacity allows, lower SOM or add headcount to the plan.
Related templates
All sales ops templatesSales capacity planning calculator
Territory & Quota
A sales capacity planning calculator that turns headcount, ramp, attrition, and realistic attainment into bookings capacity. Free PDF and CSV.
Ideal customer profile template
Enablement & Process
An ideal customer profile template built from closed-won, closed-lost, and churn data, with firmographic fields and a scoring model. Free PDF and CSV.
Account tiering model
Territory & Quota
An account tiering model that scores fit and intent to set tier and coverage, with a scoring rubric and worked examples that add up. Free PDF and CSV.