This interactive tutorial provides practice in using dimensional analysis to do metric conversions and validate the conversion factors in equations. Users are first guided through two example problems, then progress to exercises requiring self-solving. Users may click to add conversion factors or select units from a drop-down menu. Helpful tools include a "Pencil and Eraser" that allows users to draw lines for cancellation of units, and a "Balance" tool that tells the users whether their conversion factors are valid. This resource is appropriate for students of introductory physics.