The Cool Girl Formula: How to Master Effortless It Girl Style in With Three Pieces

Ellen Jones
19 hours ago
3 min read

Hailey Bieber in the Three Piece Cool Girl Style Formula: tailoring + denim + leather — thecelebrityfinder/Bauer-Griffin/GC Images/Getty Images

Getting dressed shouldn’t require a full-blown existential crisis in front of your closet. Which is why Indie Identity created The Style Formula; your indispensable shortcut to building outfits that actually work, using classic fashion archetypes, from the boho Spiritualist to the always-pool-ready Hotel Lobbyist.

Each Style Formula breaks down the DNA of a signature aesthetic, showing how three key wardrobe pieces come together to create a recognisable look. And for the Cool Girl, the formula is all about the perfect balance of relaxed and refined: lightweight tailoring with relaxed denim and slouchy leather.

It’s the outfit equation behind countless street style looks from fashion icons. Oversized blazers thrown over vintage-style jeans, oversized leather bags, lived-in accessories, and just enough polish to look like you didn’t try too hard…even if you absolutely did.

Ready to unlock your Cool Girl era? Here’s who is wearing cool girl style well, and how to dress like a cool girl with Indie Identity’s curated pieces.

Alexa Chung: The OG Cool Girl

Before “model off-duty” became a Pinterest category, Alexa Chung was defining the look. Her approach to it-girl style is rooted in vintage references, British eccentricity and pieces that look better with age.

Alexa mixes tailored elements with relaxed denim, worn-in tailored leather and unexpected details like hulking hobo bags, creating outfits that feel personal rather than overly styled. She proves that the secret to cool isn’t perfection, but character.

Her Cool Girl formula: vintage tailoring + relaxed denim + lived-in leather

Shop her Style

Firelady Fur “South City Old Lane” Vintage Aviator Leather Jacket
Firelady Fur "Poland Island" Pure Cotton Sleeveless Collar Shirt

Hailey Bieber: The Modern Minimalist Cool Girl

If there’s one person who has perfected the art of looking expensive while wearing the simplest pieces, it’s Hailey Bieber. Her signature style is built around oversized proportions, clean silhouettes and a less-is-more attitude.

Hailey’s take on the Cool Girl formula is all about contrast: an oversized blazer or leather jacket paired with relaxed denim, pared-back basics, and accessories that add just enough polish. She understands polished casual outfits need the power of a strong silhouette, letting one or two standout pieces carry the entire look.

Her Cool Girl formula: oversized tailoring + relaxed denim + polished leather

Shop her Style

Firelady Fur "Sydney Echoes" Sheepskin Jacket Blazer in Vintage Meillard Suede
Firelady Fur "Dublin" Lapel Slim Fit Short Sleeve Polo Shirt
Firelady Fur "Art Journey" Distressed Dyed Tencel Cotton Jeans

Elsa Hosk: The Scandi Cool Girl

Elsa Hosk brings a softer, more feminine interpretation to the formula. Her style combines Scandinavian simplicity with a fashion-editor edge; think playful proportions, vintage-style denim, nipped-in tailoring, and carefully chosen accessories.

Her approach proves that the Cool Girl wardrobe doesn’t have to be monochrome. Texture, shape, and subtle details are what make simple pieces feel special.

Her Cool Girl formula: sharp tailoring + vintage-inspired denim + oversized leather

Shop her Style

Firelady Fur "Berlin Afternoon Tea" Twill Linen Old Money Style Waist Shirt Top
https://www.indieidentity.com/style-identities/the-cool-girl
Metamorphoza Beige Extravagant Backpack

Kendall Jenner: The Polished Cool Girl

Kendall Jenner’s style sits somewhere between model-off-duty and quiet luxury. She takes classic wardrobe staples and gives them a sharper, more refined feel.

Her version of the formula often features clean tailoring, relaxed jeans, and elevated basics (hello, beautiful Birkins); proving that casual dressing can still feel sophisticated. She’s the master of making everyday pieces look intentional, whether it’s pairing oversized layers with denim or adding sleek accessories to a laid-back outfit.

Kendall’s wardrobe is a lesson in restraint: fewer pieces, stronger silhouettes.