Research to date has focused mostly on children's representation of their physical self as a prelude to the development of a theory of mind (ToM) and on their understanding of the self as distinct from others over time. Whether children approaching the well-known age of ToM mastery are also accurately appraising their own body's functional relationship to the everyday environment remains largely an unanswered question. Little work has investigated typical preschool-age children's explicit accuracy when making judgments about their own body's proportions. In the current study, 98 preschoolers made 16 practical judgments about whether their own body or an experimenter's body could fit through an apparatus (half of the apparatuses were 30% smaller than the body in question, and half were 30% larger). Overall, accuracy increased with age but was unrelated to body size. Children in all age groups performed above chance, and accuracy did not differ depending on target (e.g., self or other). Children in a comparison condition judging fit of inanimate objects (n = 23) performed similarly, though showed less evidence of “yes” bias, and there were no age-based differences in accuracy. Results are discussed with regard to preschoolers’ developing body awareness, as are implications for research protocols in which children are asked to accurately identify their own body size and shape from an array.