What is a size 18?How girls' and boys' size 18 compare across 23 kids' brands

A size 18 is designed with older kids and young teens in mind, but age is only a rough guide. Because it is built around height and build, plenty of children wear a size 18 a year earlier or later than the label suggests. Checking your child's height against a specific brand's chart is far more reliable than going by age alone.

Most brands cut a girls' size 18 for about 62½–66" and a boys' size 18 for about 65–67", but across brands the label covers 60–67" — that full span is the honest answer. Check your child's height against the brand you are buying.

Not always. Many brands publish one unisex size 18 that covers both, but 10 of the 23 brands here chart girls and boys separately — and where they do, the two can differ by an inch or more at the same number. The table above shows both, so you can compare the one that matches your child.

Neither, reliably — a size 18 is not standardized. Across these 23 brands it covers heights from 60 to 67", a spread of about 7 inches, so "big" or "small" only means anything next to a named brand.

No, and there is no industry standard that would make it so. Each brand sets its own size 18 height range, which is why the number cannot be carried from one brand to the next: the size that fits in one can be short or roomy in another under an identical label.

A size 18 is near the top of the kids’ range, and it doesn’t map cleanly onto one adult size. Adult XS, juniors and young-men’s sizing are separate systems cut for different proportions, so the number won’t carry over. If your child is at the top of a 18, measure them and compare against the specific adult or juniors chart rather than assuming a next size.

After a size 18, most brands move to a size 20 or adult sizing. Sizing can shift noticeably at that step, so it is worth checking the next size's height range rather than assuming it picks up exactly where size 18 left off.

When your child's height is near the top of a brand's published size 18 range, check that brand's a size 20 or adult sizing before buying — the next size's range doesn't always pick up where size 18 ends. We can't predict how long a garment lasts, so we point you to the boundary, not a guess.

Among the brands here, Calvin Klein Kids cuts the longest size 18, fitting up to about 67 inches of height. That is about published height only — it says nothing about how long the garment itself lasts.