To figure out how short your hair on the sides and back should be, you need to understand your face shape. Hairstyles and lengths suit different types of cheekbones, jawlines, chin bone, etc. Determine if your face shape is oval, rectangular, square, angular, diamond, round, or heart. Then, research hairstyles that match your shape, and the right length will ultimately highlight your best features. You should also consider how your grooming routine will fit into your day-to-day lifestyle. Think of your hairstyle in terms of how much time you have to spend on styling, money to spend on quality products, and time to revisit a barber for consistent upkeep. These small details can add up over time if your hairstyle is medium or long when it should be short or vice versa.