It's a question hairstylists and reliable friends are often asked: "Do you think I can pull off short hair?"
And now there's a short (heh) answer: The 2.25" 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.
"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" and you'd look amazing with short hair; anything more, and long locks will be the most flattering choice for you.
See how it works on Michelle Williams and Kim Kardashian:
But y'know, there's also a strong case for sacking all this stuff and just getting the hairstyle you want anyway, right?