On average, if you factor in time spent warming up, it’s going to be somewhere between 30 and 90 minutes. For the majority of people, that will be enough to get the job done. If you're training six days a week because you prefer doing shorter workouts more often, the length of each workout is going to be nearer the lower end of that range. But if you're following a 6-day split because you need a high volume of training to stimulate growth, each workout is likely to take longer, somewhere in the region of 60-90 minutes.