What Should a 13 Year Old Girl Wear for Underwear?

If you’re trying to figure out what underwear a 13 year old girl should wear, you’re not the only parent asking. It’s one of those things nobody really talks about, but it matters more than most people think. That’s actually how SugaPlum started! 🙂

At 13, girls are often somewhere in the middle: past the basics, not quite adult sizing, and very aware of comfort and how things feel. Here’s what’s actually worth knowing.

Cotton is still the right call

Breathable, soft, and gentle on sensitive skin: cotton is the default for a reason. Synthetic fabrics might look fine on the packaging but can cause irritation, especially for girls who are active or who have sensitive skin. Look for 100% cotton or a high cotton blend in the gusset at minimum.

Fit matters more than size

Teen bodies change quickly, and underwear that’s too tight around the waistband or leg openings is uncomfortable in ways girls often don’t mention; they just stop wearing it. Briefs and shorts-style cuts tend to work better than thongs at this age, both for comfort and for practicality under school uniform or sports kit.

Period pants are worth considering now

If your daughter has started her period, or is about to, period pants are genuinely useful: not as a replacement for other protection, but as a backup layer that removes some of the anxiety around leaks. Look for ones designed specifically for teens: lighter absorbency, secure fit, and a cut that works under normal clothes. They wash and reuse like regular underwear.

What about bras?

At 13, many girls need more than a crop top but haven’t grown into adult bra sizing yet. This is where a lot of parents get stuck: adult bras don’t fit, but most “teen” options offer no real support. What to look for: a proper cup shape, a band that sits flat against the body, and adjustable straps. A well-fitting bra at this stage makes a real difference to comfort and posture, particularly for girls who are more developed or active in sport.

At SugaPlum, this is exactly what we focus on. Our bras are made for girls aged 10 to 16 — proper structure and real support, not scaled-down adult styles or glorified crop tops. If you’re not sure where to start, our size guide walks you through how to measure at home.

A note on sizing

Teen sizing varies significantly between brands. If your daughter is between sizes or on the smaller end of adult sizing, it’s worth measuring rather than guessing. Underwear that fits badly tends to get pushed to the back of the drawer.

The short version

Cotton, the right cut for her body and lifestyle, period pants if she needs them, and a bra with actual structure if she’s ready for one. Nothing complicated, just things that fit and work.

So, what underwear should a 13 year old girl wear?

Honestly, I asked myself the same question. My daughter was at that stage where kids’ sizing was done but adult styles felt wrong: too much, too soon. I spent way too long in shops picking things up and putting them back down.

What I kept coming back to was simple: cotton, a cut that actually stays put, and for the days she needs a little more — something designed for her body, not just a smaller version of mine.

That’s why SugaPlum exists. Not because the market was missing another underwear brand, but because it was missing one that actually thought about this age group properly.

If you’re in the same spot I was, start with the basics and go from there. It doesn’t have to be complicated.