Market sizing is the process of estimating the customer base that an impact investment fund can reach. In the Blueprint methodology, market sizing has three components: the total addressable market (TAM), the serviceable addressable market (SAM), and the serviceable obtainable market (SOM). Market sizing serves two purposes: it helps the fund team assess and adjust its ability to serve the target market, and it provides potential investors with a tangible understanding of the strategy's scope.