How does a person make decisions across perceptual boundaries? Here, we test the account that confidence constitutes a common currency for perceptual decisions even in childhood by examining whether confidence can be compared across distinct perceptual dimensions. We conducted a strict test of domain-generality in confidence reasoning by asking 6- to 7-year-olds to compare their confidence in 2 decisions, either from the same perceptual dimension (e.g., number vs. number) or from two different perceptual dimensions (e.g., area vs. emotion). Not only could children compare their confidence across and within domains but there were no differences in their abilities to make within- and across-domain comparisons. Our findings support the idea that confidence is represented in a common format even in childhood, which could provide an account for perceptual integration in childhood that doesn't necessitate the use of language.