In light of this, Goblinworks has decided on a 4:1 game-to-earth-time ratio. This means that four in-game minutes will pass in the span of one real-world minute, one in-game day will pass in the span of six real-world hours, and so forth. This will also influence the rate of travel within the game. The team is operating under the assumption that the average human moves at three miles per hour. In-game hexes are about three-quarters of a mile from edge-to-edge, which means that it would take a real person about 15 minutes to traverse one hex. When you take into account the game's chronological dilation, though, the same journey will take an in-game character less than four minutes (assuming he can travel in a straight line), which the team says passes a basic "sanity test when considering the travel times required to cross the zones in other MMOs."
The full dev blog is chock-full of even more information than we can cram into this article, including details on how different variables (such as mounts, magic, and difficult terrain) will affect travel time and the perceived scale of the world, so if you're in the mood to have your brain addled by MMO chronomancy, head on over and give it a read.