On this website you will find a plethora of ideas of formal hair styles for medium hair. When you are searching through this site you see a number of hairstyles which can be classed as... next picture

...formal. Ideally you want to be on the lookout which is a bit special, something which wouldn't normally fit the bill of a casual hairstyle. Yes, this does look incredibly simple but I am sure you can agree that it looks great and would look even better combined with a marvellous dress should you head to a formal event or occasion.