A day walk maybe through the fields and hills of the rural countryside, nothing too taxing. A few miles with a pub stop half way along the route. Alternatively it might be out into the wilds of the mountains, a hard days climb in unpredictable weather. What you carry in your pack will vary a lot according to the type of walk, or walks, you intend to do. Ideally you want to carry only the essentials of your walk to keep the weight down, so your daypack should be comfortably big enough for all the items that you may need. There is no point carrying a large rucksack which is pretty empty, it can be uncomfortable and rucksacks have their own weight. Finding the daypack that is just about the right size is what we are aiming for.
Minimalist Travelling – Daypacks up to 30L - If you like to keep weight and size down to a minimum you should consider a small compact rucksack. Anything under 29L will ensure you do not over pack and just take the bare essentials. These are suited to day trips (as in the name) and are well suited to walkers and hikers who will be spending the day outdoors. There are also hydration compatible daypacks which give you the option of carrying a hydration system on board too! The larger end of the scale 25-30L are also suitable for weekend or overnight trips and can easily accommodate extra clothing, food & water and other essentials.