Kids' Clothing Size by Age Calculator
Convert a child's age into a general US clothing size, with typical height and weight ranges.
Reviewed by the ToolNestr Editorial Team — July 2026
How kids' clothing sizing works
Children's clothing sizes are labeled by expected age up through about 24 months (0-3M, 3-6M, and so on), then shift to toddler sizing (2T-4T) and youth sizing (size 5 and up), roughly matching typical growth charts published by pediatric health organizations. Each size band corresponds to a general height and weight range, since manufacturers cut garments to fit a child's expected proportions at that stage, not just a single number.
Because children's growth rates vary significantly, age is only an approximation — a tall-for-their-age 2-year-old may already fit a 3T, while a smaller child of the same age might still be in 18-24 month sizing. This calculator shows the general age-based size along with the typical height and weight range it corresponds to, so you can double-check against your child's actual measurements.
Size, height, and weight bands follow the general US children's apparel sizing convention used across most major retailers; individual brands can run slightly larger or smaller.
Worked example
A parent is shopping for a 3-year-old child.
Real-world context
Buying clothes as a gift for someone else's child is the classic use case, since the giver usually only knows the child's age, not their exact height and weight — the age-to-size conversion turns that limited information into a workable starting size, with the height/weight range as a sanity check against what the parents have mentioned about how tall the child is for their age.
Seasonal buy-ahead shopping (buying next winter's coat during a summer sale) also relies heavily on this kind of projection, since parents are estimating a size for a child who will have grown several months by the time the item is actually worn — many deliberately size up a full step for this reason.
Common misconceptions
"A 2-year-old should always wear size 2." Not necessarily. Toddler sizing (2T-4T) is built around expected height and weight for that age, but individual growth varies enough that many 2-year-olds fit better in 18-24 month or 3T clothing depending on their actual size.
"All brands' kids' sizes match exactly." They don't. Sizing runs noticeably large or small between budget and premium children's brands, more so than in adult clothing, since there is less standardization pressure in kidswear.
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Frequently asked questions
Is age or height a better way to size kids' clothing?
Height is more reliable, since children grow at different rates and two kids of the same age can differ by several inches. Age-based sizing is a convenient starting point, but check the height and weight range shown against your child's actual measurements when possible.
What does "2T" mean versus just "2"?
The "T" stands for toddler and indicates a cut designed for a child still in diapers, with a roomier fit through the middle, while a plain size "2" (rare) or sizes from about 4 onward without a T are cut for an older child's proportions.
Why do sizes sometimes skip or overlap, like 18-24 months and 2T?
Growth is not perfectly linear, and different brands draw the size boundaries slightly differently, so overlapping ranges like these exist to smooth the transition between infant/toddler sizing and youth sizing.
Should I size up for a growing child?
Many parents deliberately buy one size up, especially for outerwear and pants, to extend how long an item stays wearable — this calculator shows the standard-fit range, but sizing up a step is a common practical choice.