Target
Hidden category
Cat & Jack Girls' Plus / XXL (Size 18)
- Widest availability and lowest "name-brand" price
- True Plus cut for fuller tummy & hip
- Matching All in Motion size-18 activewear
- Popular prints sell out online by mid-June
Size 18 · XXL · 18 Plus · Tween activewear
Tired of “Sold Out”? The parents' real-time guide to girls size 18 & XXL swimwear
Your kid isn't between sizes. The stores are. Most brands stop swim production at size 14, leaving a gap right where growing tweens land. This page shows you exactly who still carries size 18, XXL and 18 Plus in swim and activewear, how each brand's fit compares, and links straight to the live inventory.
The “Tween Sizing Gap,” explained
Girls' swim is made in huge quantities up to size 10–12, then drops off fast. Size 18 and Plus get the smallest production runs, so they sell out first, often by June. The fix isn't waiting; it's knowing the three places that restock and the two brands cut for fuller and taller tweens. That's this list.
Short answer, in stock most reliably right now:
Target (Cat & Jack Plus), Walmart (Wonder Nation Plus 18), The Children's Place (Sugar & Jade, to size 22), and Lands' End (18 Plus). Tall and slim? Pivot to a women's XS.
Links checked June 2026 · we re-verify monthly · stock changes hourly at the retailer
We check stock at
Cross-brand sizing matrix
A size 18 is not a size 18 everywhere. Use this to cross-reference your child's measurements against how each brand actually cuts its top size.
Approximate guide. Figures are typical industry measurements for quick comparison, not exact garment specs. Cuts vary by style, so always confirm against the retailer's live size chart (linked on each brand) before you buy.
| Brand | Size tag | Chest (in) | Waist (in) | Hips (in) | Fit note |
|---|---|---|---|---|---|
| Target · Cat & Jack | XXL (18 / Plus) | 35 | 30 | 37.5 | Roomy Plus cut. Same height as a 16 but fuller through tummy and hip. Runs generous. |
| The Children's Place | Size 18 (Sugar & Jade) | 32.5 | 27.5 | 36 | Trim tween cut. Runs slim. If between sizes, size up. Extended sizes go to 22. |
| Walmart · Wonder Nation | Plus 18 | 35 | 31 | 38 | Budget Plus fit. Fuller middle, same length. Lighter-weight fabric; check lining. |
| Lands' End | 18 Plus | 35.5 | 31 | 38.5 | Long-torso, structured, UPF 50. Best for tall tweens; true-to-generous. |
| Women's XS (pivot) | XS (0–2) | 32.5 | 25 | 35.5 | Longer torso, more bust shaping, narrower hip. Best for tall, slim tweens past girls' sizing. |
Measure over light clothing: chest at the fullest point, waist at the narrowest, hips at the fullest. When a measurement falls between two brands' sizes, choose by waist and hip for one-pieces.
Where to buy: live size 18 directory
Every card links to the exact “hidden” category where the top sizes hide. Filter by the kind of store you want, then check live stock.
Walmart
Hidden category
Wonder Nation Girls Plus (7–18) · Plus 18
- Lowest price; in stock most of the season
- Dedicated Girls Plus line goes to 18
- Matching coverups & Wonder Nation Active
- Thinner fabric; fit varies by style
The Children's Place
Hidden category
Sugar & Jade Tween Swim, Size 18 (to 22)
- Trend-forward tween styles, not "little kid"
- Extended sizes run all the way to 22
- Frequent sitewide sales & bundles
- Cut runs slim, size up; biggest sizes online-only
Kohl's
Hidden category
Girls Plus 7–20 · SO & Lands' End
- Plus chart spans 4–20 in one place
- Carries both budget (SO) and premium (Lands' End)
- Kohl's Cash stacks on swim
- Swim selection thins out late in summer
Amazon
Hidden category
Girls' Plus Swimsuit · filter size 18
- Largest selection; dozens of UPF brands
- Fast Prime delivery before a trip
- Easy size-filtering and try-before-you-buy options
- Sizing varies wildly by seller, read recent reviews
SwimHer
Why it's first
A brand that makes its own size 18
- Designs only for this tween/teen size gap
- Stocks its own sizes, so far less “sold out”
- Age-appropriate coverage, tankinis & one-pieces
- One brand's styles; small-batch runs
Lands' End
Hidden category
Girls Plus Swimsuits · 18 Plus / 1X
- Durable fabric, true UPF 50, modest coverage
- Long-torso cut, ideal for tall tweens
- Mix-and-match tankini tops & bottoms by size
- Higher price; classic over trendy styling
L.L.Bean
Hidden category
Girls' Plus Swimwear (UPF 50+)
- Tough, fade-resistant fabric & generous cut
- Strong rash guard / sun-set selection
- Backed by a satisfaction guarantee
- Fewer "fashion" prints; premium price
Cabana Life
Hidden category
Girls 12–14 / XL UPF Rashguard Sets
- UPF 50+ sun-protective sets, long rash-guard styles
- Longer cut fits taller tweens well
- Great crossover into swim-team & beach activewear
- Premium price; top size caps early, check XL fit
Hanna Andersson
Hidden category
Big-Kid Girls 160 cm (≈ size 16–18)
- High-quality, long-lasting, sun-smart fabric
- Roomy Scandinavian cut; great rash-guard sets
- Holds up to heavy summer wear
- cm sizing (160 ≈ 14–16) tops out early; premium price
Old Navy
Hidden category
Women's XS One-Piece & Tankini
- Cheap, trendy, huge style range
- Longer torso suits tall tweens out of girls' sizing
- Pairs with women's XS activewear & leggings
- More bust shaping than some tweens need; hip can run roomy
Aerie / American Eagle
Hidden category
Aerie Swim · XXS / XS separates
- Buy top & bottom separately = custom fit
- On-trend styles tweens actually want
- Frequent BOGO swim deals
- Some cuts skimpy, filter for full coverage; pricier
Speedo
Hidden category
Girls 16 / Women's 28 Racing & Active
- Built for swim team, lessons & real activity
- Compression hold; chlorine-resistant fabric
- Best swim-to-activewear crossover on this list
- Snug athletic fit; limited fashion styling
Buttons open the retailer's live size-18 / Plus / XS results in a new tab. We don't hold inventory; prices and stock are set by each store and change constantly.
Same gap, same fix: activewear too
Size 18 leggings, rash guards and sports sets disappear for the same reason swim does. The good news: activewear follows the same numeric chart, so the brands above carry matching size-18 active pieces: Target All in Motion, Walmart Wonder Nation Active, and Speedo for sport. Use the same fit notes; size into Plus when the waist is the limiting measurement.
Back to the directory
Why this site exists
Built by a mom who lived the sold-out struggle
Hi, I'm Shelley, and I started TweenFit for one reason: my own daughter.
She had outgrown the kids' racks but wasn't ready for women's sizes, and every summer it was the same struggle. The size 18, the XXL, the 18 Plus in swimwear and activewear were sold out, mislabeled, or just didn't exist. I spent hours hunting across stores and “out of stock” pages to find pieces that actually fit.
So I built this site to save other parents that search. Everything here is what I wish I'd had: which brands really carry size 18, how each one fits, and direct links to live inventory. I review every brand and size on this page myself. No more “sold out.” Just answers.
Shelley · Founder & editor, TweenFit
Summer's here. Don't let “sold out” win.
Size 18 swimwear: parent questions, answered
The fit questions that send parents in circles, settled.
What size comes after girls' size 16?
Most US brands jump from girls' 16 to girls' 18 (often tagged XL to XXL), then into "Plus" or extended tween sizes (18 to 22) like The Children's Place's Sugar & Jade line. After that, the next step is a women's XS or a juniors XXS. Size 18 is the gap where many brands simply stop, which is why it sells out first.
Is a girls' size 18 the same as a women's extra-small (XS)?
Close in some measurements, but not the same fit. A girls' 18 is cut for a shorter torso with less bust shaping, while a women's XS has a longer torso, more bust room and a narrower hip-to-waist curve. For a tall, slim tween a women's XS often fits better; for a curvier tween, a girls' Plus 18 is usually more comfortable.
Why is size 18 swimwear always sold out?
Brands produce far fewer units in the top kids' sizes than in 7 to 14, so 18 and Plus sizes sell through first, usually by early summer. Buying earlier in the season and checking several retailers instead of just one is the fastest way to find stock.
What's the difference between size "18" and "18 Plus"?
Same height, different cut. A regular 18 fits an average build at that height; "18 Plus" keeps the same length but adds room through the chest, tummy and hips. If a regular 18 fits in length but is tight around the middle, size into Plus rather than going up to a 20.
What size swimsuit should a 12-year-old girl wear?
Go by measurements, not age. Many 12-year-olds wear a girls' 14 to 18 depending on build, and some have moved into a women's XS. Measure chest, waist and hips, then match to the comparison chart above. Age alone is the least reliable guide at this in-between stage.
Does size 18 activewear and leggings use the same chart?
Mostly yes. Girls' activewear such as leggings, rash guards and sports sets follows the same numeric girls' chart, so an 18 in swim usually maps to an 18 in activewear from the same brand. For fuller builds the same Plus cut applies. Target's All in Motion, Walmart's Wonder Nation Active and Speedo all carry matching size-18 active pieces.
More size & fit guides
Same mission, more of the hard-to-find sizes.
Stop refreshing one store's "sold out" page
Open the four most reliable size-18 sources side by side and grab the fit that's actually in stock today.
Check who has size 18 now