Unlike financial success, there is no clear consensus regarding how best to define and measure social impact. This HBS note written for students of the HBS, MBA, class - Business at the Base of the Pyramid, offers readers pragmatic perspectives on how the framework of the Logic Model (Theory-of-Change) may be used by businesses, nonprofits, and impact investors to assess the social value they create for their customers/beneficiaries and society. The note concludes with a brief tour of a few impact evaluation methodologies and their applications in areas such as hunger, healthcare, education, and microfinance.