At first glance, it is not difficult to estimate how much time will be needed for training. Different sources indicate different minimum training mileage required to run (rather than crawl) a marathon. On average, figures of 50-60 km per week are given as a minimum peak volume for a marathon. As always, this is an average for a spherical runner. If you, for example, still have a decent amount of bike loads, then running can be less, etc.