This research examines whether a common magnitude approximation system represents magnitude information and informs magnitude related judgements in adults. Participants were tested on magnitude comparison (e.g., which is more?) and magnitude estimation (e.g., if this is 100, what is this?) tasks relating to the magnitudes of number, surface area, loudness, and duration. Participant’s comparison (accuracy and RT) and estimation (precision and RT) performance was measured. Analyses revealed no correlations (except one) between comparison accuracy measures, and correlations between all comparison RT measures. Correlations were also observed between all precision measures and all RT measures for the estimation tasks. These results suggest that dimension specialized processes are involved in the representation of magnitude information, and that these representations might be employed in magnitude related judgements via dimension general processes for both magnitude estimation and magnitude comparison tasks.