Question: how much water for 20 km hike?
Answer: The rule of thumb is that you need to drink 3 to 6 fluid ounces of water each mile, or drink approximately every 15 to 20 minutes. That is 1/2 cup to 1 cup of water per mile. Let thirst be your first guide and drink when thirsty. The chart below will help you know how many bottles that translates into.