# Total Addressable Market

_Also known as: TAM_

**Category:** Market
**URL:** https://skiporship.com/glossary/total-addressable-market
**Last updated:** 2026-08-08

## Definition

Total addressable market (TAM) is the total annual revenue available if a product achieved 100% market share of everyone who could conceivably buy it — the theoretical ceiling, not a realistic target.

## What it means in practice

TAM is the outermost of three nested market figures. It answers a deliberately hypothetical question: if every possible buyer bought, and bought from you, how large would annual revenue be? It exists to establish whether an opportunity is structurally big enough to be worth pursuing — not to forecast revenue.

There are two ways to reach the number, and they are not equally credible. Top-down starts from a published industry figure and applies shrinking percentages, which is fast, unfalsifiable, and correctly distrusted by anyone experienced. Bottom-up starts from a countable population of buyers and a defensible annual spend per buyer, then multiplies. Bottom-up forces you to state assumptions that can be checked, which is precisely why it carries weight.

A TAM is only meaningful alongside its narrower siblings. Quoting a vast TAM without SAM and SOM signals that you have not thought about who you can actually reach, and the number becomes a liability in exactly the conversations it was meant to help.

## Formula

```
TAM = (number of potential buyers) × (annual revenue per buyer)
```

Build both inputs bottom-up. A buyer count you can source and a price you can defend beats any published market-size headline.

## Worked example

Compliance software priced at £3,600/year, sold to UK accounting practices.

- Countable buyer population: ~4,200 UK practices with 5–20 staff.
- Annual contract value: £3,600.
- TAM = 4,200 × £3,600 = £15.1m per year.

**Takeaway:** £15.1m is small for venture funding but excellent for a bootstrapped business — and because both inputs are sourced, the figure survives scrutiny in a way "the global compliance market is worth $40bn" never does.

## Common mistakes

- Quoting a top-down industry figure as your TAM. It is unfalsifiable, so experienced readers discount it entirely.
- Confusing TAM with a revenue forecast. TAM assumes 100% share, which no company achieves.
- Counting people who could theoretically use the product but have no budget authority to buy it.
- Presenting TAM alone, with no SAM or SOM to show what you can realistically reach.

## Related tool

[TAM/SAM/SOM calculator](https://skiporship.com/calculators/market-size)

## Related terms

- [Serviceable Addressable Market](https://skiporship.com/glossary/serviceable-addressable-market) — Serviceable addressable market (SAM) is the portion of total addressable market you could actually sell to given your business model, geography, language, regulation and target segment — TAM minus everyone you structurally cannot serve.
- [Serviceable Obtainable Market](https://skiporship.com/glossary/serviceable-obtainable-market) — Serviceable obtainable market (SOM) is the share of your serviceable addressable market you could realistically capture within a defined period, given your budget, team, distribution and existing competition.
- [Ideal Customer Profile](https://skiporship.com/glossary/ideal-customer-profile) — An ideal customer profile (ICP) is a precise description of the type of customer who gets the most value from your product, is cheapest to acquire, and stays longest — used to focus sales, marketing and product decisions.

## FAQ

**What is a good TAM for a startup?**

It depends entirely on your funding model. Venture investors typically look for a TAM above $1bn because they need outsized outcomes. A bootstrapped business can be highly profitable in a £10–50m TAM, where the lack of competition is often an advantage.

**Should I calculate TAM top-down or bottom-up?**

Bottom-up, always. Start from a countable buyer population and a defensible price per buyer. Top-down figures derived from published industry reports are treated as noise because the assumptions cannot be checked.

**What is the difference between TAM, SAM and SOM?**

TAM is everyone who could conceivably buy. SAM narrows to those you can actually serve given your model, geography and segment. SOM is the share you could realistically capture in a few years given your resources and competition.

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