Should I Size Up If There’s Stretch or Lycra Material?

It’s one of the most common sizing questions we hear:

“Do I need to size up if the clothing has stretch, elastane, or Lycra?”

The quick answer? Usually not.

In fact, in many cases, you may even want to size down.

But the right choice depends on the fabric composition, the garment type, and your personal fit preference. In this post, we’ll walk you through when to size up, when to stay true to size, and how Tellar.co.uk helps you make the right call—instantly and for free.

What Is Stretch Fabric?

When we say “stretch,” we’re talking about materials that contain Lycra, elastane, or spandex. These synthetic fibres are added to fabrics (usually 1–10%) to give them flexibility and bounce back.

You’ll find stretch in:

Skinny jeans
Bodycon dresses
Activewear and yoga leggings
Swimwear
Knitwear
Some blouses, trousers and suits

The presence of stretch can drastically change how a garment fits and feels on your body.

General Rule: Don’t Size Up for Stretch

If a garment contains Lycra, elastane or spandex, it’s designed to fit closer to the body. Sizing up can actually lead to:

Baggy or sagging areas (especially at the waist or underarms)
Loss of shape
Less support or compression

Unless a garment runs small or you specifically want a looser fit, it’s best to stick with your usual size—or even consider sizing down slightly for a sleeker silhouette.

Examples by Clothing Type

Let’s break it down further by garment category:

1. Jeans with Stretch

Most high-street jeans now contain 1–5% elastane. Brands like Zara, Mango, and Massimo Dutti often use stretch denim.

If the jeans are high-stretch skinny jeans (e.g. 5% elastane):
✅ You can usually size down, as they mould to your body.
If they’re low-stretch or rigid denim with minimal elastane:
⚠️ Stick to your normal size—or even size up if they’re tight at the waist.

✅ Check your perfect jean size by brand here:

👉 www.tellar.co.uk/store-size-lookup/

2. Bodycon Dresses

These are designed to fit like a glove. They typically contain a good amount of stretch for movement.

Want a figure-hugging look?
✅ Stay true to size or size down
Prefer a more modest or relaxed fit?
⚠️ Size up—but know you may lose some structure

3. Activewear and Swimwear

Here’s where stretch is essential—support, shape retention and compression rely on elastane.

Always stay true to size for best performance
Sizing up can cause sagging, slipping, or reduced support

4. Stretchy Trousers or Workwear

If a structured garment includes a little stretch (e.g. 2% elastane), it’s typically just to improve comfort.

Don’t size up automatically
Use Tellar.co.uk to check how the brand's sizing actually runs based on fabric and cut

When You Might Consider Sizing Up

There are a few exceptions. Consider going up a size if:

The fabric has very little stretch (under 2%)
You’re buying a body-hugging piece and want more movement
The garment has stretch in some areas only (e.g. waistband only)
You’re buying from a brand known to run small (like Zara or & Other Stories)
You’re between sizes and prefer a looser fit around key areas like hips, bust or shoulders

Not sure? Let Tellar.co.uk analyse the brand and fabric for you.

The Tellar Advantage: Size by Fabric, Fit, and Brand

Tellar.co.uk is the UK’s leading free sizing tool. It doesn’t just match your body to a size—it looks at:

✅ Fabric content (including % stretch)

✅ Brand-specific sizing data

✅ Garment cut (structured vs loose)

✅ How the item fits across the bust, waist, and hips

Whether the dress has 10% Lycra or none at all, Tellar takes it all into account and shows your best fit instantly—so you don’t have to second-guess or return again.