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Does the Brand IRO Run Big or Small? What Is Their Sizing Like and What’s Good to Buy?

Author: Stylist and brand team at Tellar

Date: 2025

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IRO is the epitome of edgy Parisian cool—effortlessly balancing luxury with an urban, undone aesthetic. From sharp-shouldered jackets to distressed tees and silk slips, the brand is beloved by fashion insiders and street style stars alike. But when it comes to shopping online, there’s one thing that trips people up again and again: Does IRO run big or small?

✦ At Tellar.co.uk, we’ve analysed every single brand’s size data, including IRO, and matched it perfectly to your measurements—so you never have to check a size chart again. With a free measuring tape, a one-time quick setup, and access to your correct size in 1,500+ brands anytime you need it, Tellar is always free to use, no catches.

👉 Try it here


What’s the Fit Like at IRO?

IRO’s sizing tends to vary depending on the garment category, but overall it leans toward a slim, French fit—tailored but not tight, often with a touch of ease in the silhouette. However, IRO sizing can feel small if you're used to UK or US high-street brands.

Key observations:

  • Jackets and blazers often fit true to size but are cut narrow in the shoulders.

  • Tops and dresses are frequently slim through the bust and waist.

  • Trousers and denim tend to be low-rise or mid-rise, requiring careful size checking.


IRO Women's Size Guide (Approximate UK Equivalents)

IRO Size

UK Size

Bust (cm)

Waist (cm)

Hips (cm)

34

UK 6

80

60

86

36

UK 8

84

64

90

38

UK 10

88

68

94

40

UK 12

92

72

98

42

UK 14

96

76

102

Many customers say IRO runs ½ to a full size small, especially in fitted styles and structured jackets. Tellar handles this nuance for you.


Fit Insights from Real Shoppers

  • “IRO jeans looked amazing but ran small in the waist—I had to size up.”

  • “Their jackets are narrow in the arms, but the body fit is perfect once you go up one size.”

  • “My usual UK size 10 felt tight in their silk slip dress—needed a 40.”

With Tellar.co.uk, you won’t need to rely on trial and error. We calculate your best-fitting size based on your body—not just your label history.


Best IRO Pieces Worth Buying

IRO is known for balancing rugged coolness with refined design. Here’s what’s worth investing in:

1. The Ashville and Han Leather Jackets

IRO’s iconic leather jackets are a cult classic. With buttery lambskin and narrow shoulders, these fit best when sized correctly—Tellar helps avoid costly sizing mistakes.

2. Tailored Blazers and Coats

Their double-breasted coats and cropped blazers offer sharp tailoring in minimalist palettes. Best for those seeking versatile investment pieces.

3. Silk Dresses

IRO’s slip dresses, asymmetric hems and ruched detailing are signature to their aesthetic—beautiful but unforgiving if you get the size wrong. Tellar ensures a precise fit.

4. Distressed Tees and Knitwear

Their luxe basics—often featuring raw edges or slouchy cuts—are easier to fit, but you’ll still want the right size to avoid drowning in fabric or pulling at seams.


How IRO Compares to Other Brands

If you’re switching from brands like Zara, AllSaints or Reiss, IRO may feel more fitted. It’s essential to avoid making assumptions based on your UK size alone.

For comparison, check out:


Why Is IRO Sizing Tricky?

  1. French Sizing Origins:

    IRO uses French sizing labels, which are often one full size smaller than UK equivalents.

  2. Fabric + Fit Type:

    Items made of rigid leather, silk, or wool blends will feel tighter than cotton or jersey basics.

  3. Cut:

    Many styles feature drop shoulders, cropped lengths, or high armholes—making fit more complicated than simply choosing a UK size.

Tellar handles all of these factors in real-time based on your measurements.

👉 Find your IRO size now


Stop Guessing—Use Tellar to Get It Right

Tellar.co.uk is the UK’s leading fit tool for clothing. We’ve created a platform that removes all sizing guesswork by combining:

  • Your body measurements

  • A deep database of brand-specific sizing data

  • Garment-by-garment variations

With Tellar, you can:

  • Match your exact size across 1,500+ brands (including IRO)

  • ✅ Get a free tape measure posted to you

  • ✅ Set up once and use it forever—your profile stays saved

  • ✅ Know when a brand runs small, large, or true to size

  • ✅ Use from desktop or mobile—no download required

It's 100% free, and we never show ads or sell your data.

👉 Create your Tellar profile now

👉 Or check your size in IRO instantly


Other Articles to Read Next

Want more help navigating luxury sizing and fit? These Tellar guides break it down:


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We’re constantly adding more brands and refining our fit logic—so your size is always accurate, wherever you shop.


Final Thoughts: IRO Sizing Runs Small—But That Doesn’t Have to Matter

If you’re shopping IRO, just know that their sizing isn’t always UK-friendly. But with tailored jackets, elevated basics, and statement dresses—it’s worth getting right. The good news is: you don’t need to guess.

Use Tellar.co.uk to:

  • Instantly see your best-fitting IRO size

  • Avoid returns and fit disappointment

  • Access your size for 1,500+ brands anytime

Find your size in 1,500+ brands real-time. It’s free & easy.

👉 Start now at Tellar.co.uk

Does the Brand IRO Run Big or Small? What Is Their Sizing Like and What’s Good to Buy?