Plate waste is the food left uneaten on diners’ plates and cleared to the bin, a metric that good restaurants monitor closely. High plate waste signals problems: portions too large, dishes that disappoint, or menus misaligned with customer expectations, and each wasted plate erodes margins twice, in food cost and in disposal. Systematic measurement, weighing waste by dish, lets kitchens adjust portion sizes, reformulate unpopular items, and redesign menus around what is actually eaten. Beyond economics, plate waste is an environmental and ethical issue, contributing to the vast stream of food waste with its embedded carbon, water, and labour. Strategies to reduce it include offering portion choices, improving dish quality so plates come back clean, and donating or repurposing safe surplus, turning a loss line into a management tool.