It is just large enough to hold everything I need, without being uncomfortable and bulky.  I have two small children and take snacks, drinks and a change of clothes everywhere I go.  It has enough pockets on the outside that I can carry my cell phone, camera, etc. and don't need a purse in addition.  I use it for every outing we go on, Disneyland, the aquarium, the zoo, the park, etc.