Should I Size Up in Swimwear?

Why swimwear sizing gets complicated

Here’s the thing about swimwear that makes it different from your everyday clothes: it needs to work in water.

This means it generally fits more snug than your regular wardrobe favourites. When fabric gets wet, it can stretch and sag, so a suit that feels perfectly comfortable on dry land might end up loose and unsupportive once you hit the water. That’s why most swimwear is designed with a bit of compression and a tighter fit than your average tee or dress.

Think of it this way: your swimmers need to hug you just enough to stay put during that perfect dive. Too loose, and suddenly, your nips aren’t where you left them.

When you might want to size up

While a snug fit is generally best for swimwear, there are times when sizing up makes sense:

If relaxation is your top priority: Some of us simply prefer a more relaxed feel with less compression. If firm-fitting swimwear feels uncomfortable or restrictive, going up a size can give you extra breathing room.

If your body tends to fluctuate: Bodies change—during your cycle, throughout the year, or even from one day to the next. If you experience regular fluctuations, a slightly larger size might accommodate these changes more comfortably.

For certain styles with less stretch: Some styles, particularly those with structured elements like underwires or moulded cups, might feel better with a little extra room. 

For longer torsos: If one-pieces tend to dig into your shoulders, ride up, or feel too short, sizing up might give you the extra length you need for a comfortable fit.

When to stick with your measured size (or even size down)

Sheila’s swimsuits are designed to be snug and supportive, molding to your body over time. That means a closer fit is often best. Here’s when to trust your measurements and avoid sizing up:

For water activities: If you’re planning to swim, surf, or move actively in your swimmers, a properly fitted suit is essential. Remember, most swimwear fabrics will give slightly in water.

For maximum support: Particularly for larger busts, the right fit ensures you get the support you need. Sizing up too much can reduce the design’s supportive benefits.

When the fabric has excellent stretch: Our swimsuits are crafted from premium, high-stretch fabrics that adapt to your body while holding their shape. This means they provide a flexible, secure fit that moves with you—without the need to size up.

A note on fit: If you’re between sizes, choosing the smaller size usually results in a better fit that stays secure in the water. 

Finding your best Sheila fit

Rather than focusing on what size you "usually" wear (because we all know sizing is wildly inconsistent across brands), we recommend using these guidelines:

Use our size chart: Measure yourself and compare to our size guide. These measurements are specific to Sheila styles and will give you the most accurate starting point.

Consider your fit preference: If you're between sizes, think about whether you prefer a more sculpting, secure fit (go with the smaller size) or a more relaxed feel (opt for the larger size).

Think about the style: Different pieces in our collection may fit slightly differently. Our swim shorts, for instance, are designed to stay in place without riding up—something that requires a proper fit.

Trust the fabric: Our high-quality, recycled nylon fabric is designed to offer just the right amount of stretch while maintaining its shape. It will mould to your body over time for a personalised fit.