The paper deals with the dependence of the share of households’ food expenditure on the total expenditure and the household’s size. This problem is important in applied welfare economics. According to the Engel’s law, the poorer household, the greater proportion of its total expenditure is devoted to the food consumption. In the study, the Working-Leser model was applied to Polish households microeconomic data from 2000, 2005 and 2009.