Formula for rough amount of water to carry on hike?

Question

Is there a formula which can be used (I'm thinking one that gives amount of water needed factoring in time or distance covered and temperature) to roughly work out the amount of water that needs to be carried for a particular hike?

Obviously this will be a very rough guide - I know how much I generally drink, but I tend to drink quite a lot, I'm wondering as a rough approximation I can give to others to form an idea in their head.

Is there an "official" such formula, or have others coined their own that they use?

Answer 1

The rule is 3 liters per person per day. You may get away with 2 liters if it's not too hot and you stay moderate. Keep into account that your "normal day" intake is skewed by the contribute brought from food. If you eat food with less water in it, which is likely during a hike, your need for actual water is higher than the one you experience in your daily life. Add the physical activity and you get the idea.

Answer 2

I walked Hadrian's Wall recently carrying an 18kg backpack. It was hot, sunny weather for six of the seven days. I had a 2 litre bladder of water and by the end of each day I had ran out of water. That was not a nice feeling walking the last couple of miles without water. I have now upgraded to a three litre bladder.