In two experiments, we investigate how adults think about proportion across different symbolic and spatial representations in a comparison task (Experiment 1) and a translation task (Experiment 2). Both experiments show response patterns suggesting that decimal notation provides a symbolic advantage in precision when representing numerical magnitude, whereas fraction notation does not. In addition, pie charts may show some advantages above number lines when translating between representations. Lastly, our findings suggest that the translation between number lines and fractions may be particularly error-prone. We discuss what these performance patterns suggest in terms of how adults represent proportional information across these different formats and some potential avenues through which these advantages and disadvantages may arise, suggesting new questions for future work.