Our study shows that the Mothers' Milk Tool can be used to estimate per child volumes and values of breastmilk produced and lost at local levels, and to provide simple indicators of the effects of breastfeeding interventions using the percentage of lost breastmilk, where datasets on rates of breastfeeding by month of age are available. The results of such studies can be used to advocate for better and adequately funded programmes for the protection, promotion and support of breastfeeding.