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Purpose Routine, systematic measurement of food waste in acute care hospitals is challenging, particularly when monitoring plate waste at scale. This study examines the accuracy of a digital photography method for measuring aggregate solid-food plate waste across hospital mealtimes, with the aim of determining its suitability as a practical, scalable tool for ongoing monitoring. Design/methodology/approach Plate waste was assessed across seven breakfasts (n = 108), 21 lunches (n = 804) and 21 dinners (n = 851), reflecting the full hospital menu cycle (one-week rotation for breakfast and three-week rotation for lunch and dinner). For each meal, waste was measured using both direct weighing and visual estimation based on a 7-point scale applied to pre- and post-consumption photographs. Waste quantities for individual solid-food components were calculated by multiplying visually estimated leftovers (%) by standard serving sizes. Agreement between methods was assessed using Bland-Altman plots and Spearman correlation. Findings Digital photography estimates showed a strong positive correlation with direct weighing across all mealtimes (rs = 0.9895, p < 0.001), with consistently high agreement at breakfast, lunch and dinner (all p < 0.001). Overall, the mean difference between methods was 4.67 g, with limits of agreement from −50.51 to 59.84 g. Breakfast showed the highest accuracy, while lunch and dinner showed slightly wider limits. Findings support digital photography as a valid and efficient alternative to direct weighing for monitoring solid-food plate waste, with greatest accuracy at breakfast. Originality/value Digital photography offers practical advantages by reducing labour, time and spatial requirements, supporting its feasibility and sustainability for routine plate waste monitoring.