It’s a question we as hairstylists are often asked: “Do you think short hair will look good on me?” Thanks to the legion of celebs recently liberating their locks with crops, bobs, and lobs, short hair is hotter than ever.

Well the question of flattery has a short answer: The 2.25-inch rule.

The magic measurement was discovered by hairstyle trendsetter and product innovator John Frieda, and “it’s all about the angles,” says Giles Robinson, senior stylist at John Frieda Salons UK and international training director of Colour Wow.

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John studied faces and saw that the angle of the jaw bone determined whether or not someone would look best with short hair or long hair. They say the result is a trusted, easy but exact measurement that indicates whether a face (any face) is suited to short or long hair.

To try it, position a pencil or pen under your chin horizontally and then place a ruler under your ear, vertically. Take your measurement from the intersection of the pencil and ruler. Less than 2.25 inches and you’d look amazing with short hair, and if it’s anything more, long locks will be the most flattering choice for you.

It works well with Michelle Williams and Kim Kardashian, and when you think of other obvious examples such as Audrey Hepburn next to Sarah Jessica Parker, it becomes crystal clear. (Those faux bob hair-tuck selfies are now a thing of the past.)

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