Companies that are building networks need to sell to two types of customers. For example, advertising networks sell to both owners of inventory (e.g., websites) and advertisers. As a result, the addressable market for a network needs to reflect both customer segments and is constrained by the smaller of the two.

If a company has enough advertising money committed to generate $100M, but can only access enough inventory to generate $50M, the company’s total addressable market is $50M. The company simply can’t take advantage of all of the available ad dollars. Similarly, if it has lots of inventory buy not enough ad dollars, it would quantify its addressable market as the smaller number.

The addressable market calculation for each side of the network should be handled the same way any other opportunity would be sized. See my prior post Addressable Market: Making The Estimate for details on the process.