Kids Costume Sizes Explained: Toddler to Teen
Kids' costume sizes look simple until you have two tabs open and one says "Medium (7-8)" while the other says "Medium (8-10)." Costume sizing is not clothing sizing: most labels are age ranges set by each manufacturer, and the same letter can cover different ages on different costumes. This guide decodes every size you'll see across our baby, toddler, kids' and teen costumes, using the exact wording from our product pages. Prices are current at time of writing.
Baby costumes are sized in months
Infant costumes use age-in-months ranges. The most common set is 0-6 Months, 6-12 Months and 12-18 Months; the Baby Star Wars The Mandalorian Grogu Costume ($51.99), for example, is sold in all three. Some pieces run to 18-24 Months, such as the Baby Santa Suit Costume (6-12 and 18-24 Months). Bunting-style costumes, the one-piece sacks with a face opening and arm openings, are often listed as a single size, like the Baby Bacon Bunting Costume ($30.99), "Size 3-9 Months." Babies grow fast, so if a Halloween or Christmas photo is a month or two away, read the range with that date in mind, not today's.
Toddler sizes: 2T, 3T-4T and 4-6X
The "T" stands for toddler, and it follows the same number scale as toddler clothing. Our toddler costumes are most often sold in 2T and 3T-4T (sometimes written 3T/4T), and a few start at 18 Months-2T. Where a costume runs bigger, the next step is 4-6X, which bridges toddler and little-kid sizes. The Toddler Bluey Adaptive Costume ($60.99) shows the full run on one page: 2T, 3T-4T and 4-6X, with front Velcro closures and long wrist and ankle openings for easy on and off. Many toddler pieces are over-the-head tunics, like the Toddler Shark Halloween Costume ($43.99, 2T and 3T-4T), which is designed to pair with your own pants and shoes, so exact length matters less than the tunic fitting over the head and shoulders.
Kids' Small, Medium and Large: read the numbers
This is where parents get tripped up. Our kids' costumes use two different letter systems, and the product page always prints the numbers next to the letter:
- Small (4-6), Medium (7-8), Large (10-12): used on costumes such as the Kids Deluxe Super Mario Bros Toad Costume ($66.99).
- Small (4-7), Medium (8-10), Large (12-14): used on most of our licensed superhero and Star Wars costumes, such as the Kids Value Star Wars The Mandalorian Costume ($33.99).
Some novelty costumes use a two-step system instead, like Small (4-6) and Medium (7-10) on the Boy's Grandpa Costume ($42.99), and some single-size tunics say simply "Kids small, size 4-6" or "Kids medium, size 7-10." The numbers are the manufacturer's age range. A "Medium" child in one brand may be a "Small" in another, so ignore the letter you bought last year and match the numbers to your child's age and build.
When a page lists height and weight, use it
A handful of costumes publish measurements instead of ages, and those are the most reliable guides we can give you. The Kids Sumo Hoopster Costume ($48.99) is listed as Kids medium, height 49-57 inches and weight 52-83 pounds. Teen inflatables such as the Teen Red Inflatable Crewmate Killer Costume ($41.99) are listed by height: "fits heights from 5 ft. 1 in. to 5 ft. 9 in." When you see a line like that, measure your child rather than guessing from age.
Teen sizes
Teen costumes are usually one size with an age range. The Teen Penguin Costume ($53.99) is "one size fits most teens (13-16)," and other teen tunics carry the same 13-16 label. For a smaller teen, a kids' Large (12-14) may overlap; for a taller one, look at adult costumes and read the size line on each page.
How to measure your child
Take three numbers with a soft tape while your child stands straight. Height: heel to top of head, no shoes. Chest: around the fullest part, under the arms. Waist: around the natural waistline. Write them down with the date. Then compare to the product page: if it gives height and weight, use those; if it gives only an age range, use your child's age and whether they typically wear their age size or a size up in regular clothes. We don't publish measurements beyond what the manufacturer lists, and we won't invent a rule about sizing up or down that isn't on the page. If you're unsure, ask us before you order.
Why the right size matters more with costumes
Under our refund policy, costumes are returnable only in unopened, unblemished original packaging, within 30 days of receipt, with customer service authorization first, and refunds exclude return shipping and a 15% restocking fee. That means you can't try it on and send it back. A measured child and a careful read of the size line is the cheapest insurance there is, and it leaves more time for the fun part: watching them run to the mirror.
Frequently Asked Questions
What does 3T-4T mean in a costume size?
The T stands for toddler. A 3T-4T costume is cut for children who wear toddler size 3T or 4T in regular clothing. Our toddler costumes are most often sold in 2T and 3T-4T, with some running to 4-6X.
Why is Medium 7-8 on one costume and 8-10 on another?
Different manufacturers use different age ranges for the same letter. Our kids' costumes use either Small (4-6), Medium (7-8), Large (10-12) or Small (4-7), Medium (8-10), Large (12-14). Always match the numbers printed next to the letter, not the letter itself.
What size costume does a 6-year-old wear?
Depending on the costume, a 6-year-old falls into Small (4-6), Small (4-7) or, for toddler-style pieces, 4-6X. Check the exact range on the product page, and if the page lists height and weight, measure your child instead of using age.
Can I return a kids' costume that doesn't fit?
Costumes are returnable only in unopened, unblemished original packaging within 30 days of receipt, with prior authorization from customer service, and refunds exclude return shipping and a 15% restocking fee. Once the package is opened it cannot be returned, so measure first.