When hairstylist Orlando Pita sheared Amanda Seyfried’s heavy waist-length mane into a sassy, shoulder-grazing style in July, the petite, 5-foot-3 starlet morphed from Cousin Itt to It girl with the snip of his scissors.

“She’s got gorgeous, amazing hair,” Pita tells The Post. “But for her height, proportionally, that long, long hair overpowers her. I wanted to be able to pick up her hair and have little pieces hanging that look like they fell out of a ponytail — kind of sexy and haphazard.”

And how does the straight-talking actress feel about the chop?

“I f - - king love it!” she told People magazine in September.

Seyfried is rocking a “midi,” the hottest cut in Hollywood. Falling somewhere between the collarbone and the armpits, the swingy ’do frames the face and lightens the silhouette without losing the sensuality of long hair. While the intermediate length isn’t new — Rita Hayworth and Lauren Bacall were early adopters — today’s versions are layered for movement and often topped with bangs.

Seyfried isn’t the only boldface beauty crushing on the midi: More than a dozen celebs flaunted medium-length locks at the Golden Globes last week, including Jennifer Lopez, Kate Hudson and Rosie Huntington-Whiteley, sealing its red carpet status.

Even Kate Middleton, Duchess of Cambridge, lopped a few inches off her crowning glory in December, paving the way for pregnant newlywed Princess Sofia of Sweden to do the same a few weeks later.

Celebrity stylist Jen Atkin, the talent behind Khloé Kardashian’s long bob, says the style is appealing because it’s different without feeling like a drastic change.

“It’s a great cut for the new year — you can symbolically and literally get rid of those dead ends and start fresh,” says Atkin, the founder of Ouai Haircare, which launches online in February. “It looks great on everyone. The key is layering it right for your hair type and face shape.”

The midlength is easy to blow out, and its length lends itself to a variety of styles. “You still have the option of pulling it up, wearing it in a ponytail, wearing it natural, wearing it dead straight,” says celebrity stylist Garren, who shapes Karlie Kloss’ silky midi. “I think long hair has run its course.”

The midi’s dangers lie in it looking “too done” — a grave insult in the upscale salon world, where perfectly imperfect is the goal.

The trick to keeping it fresh, according to Atkin, is to give it an “edgy, lived-in finish.” She preps damp hair with Ouai Wave Spray and Hair Oil, blow-dries with a paddle brush, then uses the Kardashian Beauty 3-in-1 iron to create a wave with straight ends. She breaks it up with Ouai Finishing Cream and seals the deal with her Soft Hair Spray.

The low-maintenance midi is ideal for commitment-phobes. “It’s a great baby step,” says Atkin. “If you don’t like it, it will grow back fast.”