This bag is a great size for everyday use. It's not too big, but it's not small either.
It measures 14 inches by 19 inches by 7 inches, so you can fit a lot of stuff in it!
It's the perfect size to carry around with you on the weekends when you don't need to carry much.
The shoulder strap is adjustable, so if you're looking for a smaller shoulder bag, this one will work well for you! 

 Size: Upper length / lower length*height*width=14/19*20*7cm