ViaMichelin shows the exact distance between Mainz and Darmstadt, based on the route selected. ViaMichelin will help you to determine the best route based on various options and, by default, offer two to three routes with varying costs, distances and journey times. Some routes (e.g. the cheapest) may suggest quieter roads or avoiding tolls whilst others will offer a compromise between distance, travel time and cost for your journey between Mainz - Darmstadt.
