Understanding the magnitude of food loss and waste (FLW), and where in the value chain it occurs, can provide policy perspectives for targeting innovations and business opportunities to reduce FLW. Since the seminal 2011 Food and Agriculture Organization (FAO) report on global FLW and the adoption of the UN Sustainable Development Goal (SDG) 12.3 (By 2030, halve per capita global food waste), there has been a surge of research efforts quantifying FLW in recent years. However, there is disagreement over how best to measure FLW. Without reliable data, it will be challenging to derive policy and action that target FLW hotspots. In this synthesis, we review the available tools for measuring FLW, their advantages and disadvantages, and comprehensively assess their ranking in terms of accuracy, cost, and meaningfulness. The methods for quantifying FLW may vary according to the stages and types of a food supply chain, for which different resources and technical capabilities are required. Therefore, a strong call to standardize FLW quantification methodologies is imperative in order to harmonize measurement tools and methods.