How to Choose Girls Swimwear Size: The Quick Guide With No Guessing

How do you choose girls swim wear sizes? Swimwear sizing for girls is nothing like clothing sizing. The numbers don't match. The measurements matter more. And getting it wrong means a return trip to the post office instead of heading straight to the beach.

If you've ever bought a girls' size 12 dress that fit perfectly, then ordered a girls' size 12 bikini that didn't, you know exactly what I'm talking about. Every brand runs differently. When you're shopping for a tween (sizes 8–14), whose body is changing fast, the guesswork feels even more stressful.

Here's the good news: learning how to choose girls swimwear size takes about two minutes. All you need are three measurements, the brand's size chart and one simple rule: trust the numbers, not the label.

Let's walk through it.

How to choose girls swimwear size ?

Girls' clothing sizes are all over the place. A size 12 in one brand might be a 10 or a 14 in another, especially when you're shopping online.

Swimwear is even trickier. Unlike a t-shirt that can stretch or shift a bit, a swimsuit needs to fit snugly across the bust, sit securely at the waist and stay in place through movement and water. Too loose, and she'll feel uncomfortable and self-conscious. Too tight, and it's restrictive.

For tweens, this matters even more. Their bodies are changing rapidly. A girl who's a size 10 in winter might be a size 12 by summer. Growth spurts happen fast at this age, which is exactly why tween-specific sizing exists.

This is why tween swimwear Australia brands like Sorbae were created. We're not scaling down junior women's sizes or inflating kids' sizes. We're designing specifically for girls ages 8–14, whose proportions and fit needs are completely different.

The Three Measurements You Actually Need

Forget generic size charts. To learn how to measure for girls swimwear, you need three key measurements: bust, waist and hips.

Bust: Measure loosely around the fullest part of the chest, keeping the tape measure parallel to the ground. Don't pull tight. The tape should sit flat and comfortable, as if it's just resting there.

Waist: Measure around the narrowest part of the torso, usually just above the hip bone. Keep the tape measure relaxed. You should be able to slide a finger underneath without resistance.

Hips: Measure around the fullest part of the hips and bottom. Stand with feet slightly apart, and keep the tape parallel to the ground.

Write all three numbers down. You'll compare them to the brand's specific size chart, not a generic girls' swimwear guide, but the actual measurements provided by the company you're buying from.

How to Read a Size Chart (And Why It Matters)

Every brand's size chart should list measurements for each size in their range. For tween sizes (8, 10, 12, 14), the chart should include bust, waist and hip measurements.

Here's the important part: compare all three of your measurements against the chart, not just one. If your daughter's bust measurement is a size 10 but her hip measurement is a size 12, she's between sizes.

When that happens, you have two options: size up or size down. The choice depends on which measurement matters most for comfort. If the bust is significantly snug, size up. If the hips feel loose, size down. There's no perfect answer, but this is where your instinct and the brand's fit notes come in.

Many brands, including Sorbae, include fit guidance on their size charts. Read it. It's there for a reason.

Common Swimwear Fit Mistakes (And How to Avoid Them)

We see it all the time: parents ordering swimwear using their daughter's regular clothing size.

This is mistake number one. Your daughter might be a size 12 in jeans. That doesn't mean she's a size 12 in swimwear. Measure instead of assuming.

Mistake two: Ordering based on age, not measurements. A 12-year-old is not automatically a size 12. Growth rates vary wildly at this age. Some girls shoot up early. Others fill out gradually. Measurements are your only reliable guide.

Mistake three: Ignoring the rise (the distance from the waistband to the leg opening on bottoms) or the length. Swimwear length affects fit enormously. A suit that's too long will bunch and shift underwater. One that's too short will feel uncomfortable or leave her self-conscious.

Mistake four: Not reading the fabric content or care instructions. Chlorine, salt water and sun all affect swimwear differently. Knowing what you're getting and how to care for it extends the life of the suit and keeps it looking great all summer.

The solution to all of this? Slow down. Measure carefully. Read the size chart. Check the fit notes. Then order with confidence.

Tween Swimwear Sizes 8, 10, 12, 14: What Size Should Your Daughter Wear?

There's no magic formula here, but there are general starting points.

Girls in size 8 are typically ages 7–9, with measurements in the 20–22" bust range. Size 10 tends to fit girls ages 9–11 (bust 22–24"). Size 12 covers ages 11–13 (bust 24–26"), and size 14 fits girls ages 13–15+ (bust 26–28"+).

These are rough guidelines. Your daughter might be outside these ranges entirely, and that's completely normal. Again: measure, don't guess.

If she's between sizes, consider her activity level. Is she a strong swimmer who moves a lot in the water? Size down slightly for security. Is she more of a lounger by the pool? Size up for comfort and room to grow.

What Size Swimsuit for a 12-Year-Old Girl?

This is one of the most common questions we hear, and it has no single answer because every 12-year-old is different.

Some 12-year-olds are still in a size 10. Others are in a 14. The only way to know is to measure.

That said, if your daughter is a typical 12-year-old with average growth, she's probably in a size 12 range. But "probably" isn't good enough when you're ordering online. Measure her bust, waist and hips, and compare those numbers to the brand's size chart.

If she measures as a 12 across all three measurements, order a size 12. If she's between a 12 and a 14, read the fit guidance or reach out to the brand. Most are happy to help.

The Between-Sizes Conversation: When Your Daughter Is In-Between

Tweens' bodies don't fit neatly into size boxes. It's frustrating, but it's also completely normal.

If your measurements show your daughter is between two sizes, you have options. Many parents choose to size up for longevity—the suit will fit for longer as she grows. Others prefer the security of a slightly snug fit for movement in water.

Neither is wrong. It depends on your daughter's body, her confidence level and how long you expect the suit to last.

Pro tip: if you're ordering from a brand that offers a detailed tween bikini size guide, read it carefully. Many brands include fit notes specific to in-between sizing.

Why Returns Happen — And How to Avoid Them

The most common reason for swimwear returns? Sizing mistakes. A suit ordered in the wrong size, or one that arrived and didn't fit as expected.

The second most common reason? Not checking the fit in person before removing the hygiene liner. Most brands, including Sorbae, offer 30-day returns with the sanitary seal intact. That means you can inspect the suit when it arrives, confirm it fits, and only then remove the tag.

Taking the time to measure correctly, check the size chart and understand how to choose girls swimwear size before you order saves everyone the hassle of a return.

Right Size. First Try. Here's How

Sorbae swimwear is designed specifically for tweens, sizes 8–14. Hand-beaded detail on every suit. Three summer-perfect colour stories: Hibiscus Crush, Limoncello Love and Sea-foam Kiss. Each style includes a detailed size chart with bust, waist and hip measurements, plus fit notes to guide your choice if your daughter is between sizes.

We know tween sizing is tricky. That's exactly why we designed our size guides the way we did. Compare your measurements to ours, read the notes and order with confidence.

Shop the Collection

Frequently Asked Questions

Should I measure my daughter myself, or have her measured at a shop?

You can do either. If you're shopping online, measuring at home is perfectly fine. Just make sure the tape measure is relaxed and you're measuring the three key areas (bust, waist, hips). If you prefer expert help, many Sunshine Coast retailers and department stores offer fitting services. For Sorbae, measuring at home and comparing to our size chart works beautifully.

My daughter is between two sizes. Which should I choose?

It depends on two things: her comfort preference and how long you want the suit to last. If she prefers a snug, secure fit for swimming, size down. If she likes room to move and wants the suit to last longer as she grows, size up. Check the brand's fit notes. Many include guidance for in-between sizing.

Can I use my daughter's clothing size to pick her swimwear size?

Not reliably. Clothing sizes are inconsistent across brands, and swimwear has different fit requirements. Always measure and compare to the swimwear brand's specific size chart, not her regular clothing size.

What if the swimwear doesn't fit when it arrives?

Most brands, including Sorbae, offer 30-day returns if the sanitary seal is intact. That means you can open the package, check the fit and size, and return it if needed. Allow 3–5 days for postage on returns and exchanges.

Do tweens grow out of swimwear quickly?

They can. Tween bodies change fast. If your daughter is at the younger end of the tween range (8–10), you might expect a season or two of wear before she needs a new size. If she's 12–14, growth may be slower. Buying a size up when she's between sizes is one way to extend the life of the suit.

Is there a best time of year to buy tween swimwear?

Sorbae's Launch Special offers Buy 2 Get 1 Free, plus a free Bikini Swim Bag with every order. It's a great time to stock up on multiple suits if your daughter has a full summer of swimming ahead, or to grab gifts for birthdays or holidays. Free shipping applies across Australia and internationally.

What's included with every Sorbae order?

Every order includes a free Bikini Swim Bag. Free shipping applies Australia-wide and internationally. Allow 3–5 days for postage. All Sorbae swimwear comes with detailed size guidance and fit notes to help you get it right the first time.