The goal of Chapter 3 is to impart the knowledge and tools for measuring happiness to the student for their own personal lives and a shift in economic systems from GDP and economic growth to happiness metrics and the well-being and sustainability of the planet. The chapter explains why and how happiness and sustainability are measured. Using analogies and thought experiments, it explores how data for satisfaction with life, affect and eudaimonia could be used for policy purposes. Through highlights, the connections between sustainability and happiness, change agency and happiness measurements, and four kinds of happiness (hedonism, eudaimonia, flow and chaironic happiness) are explained.