Size charts April 25, 2026 9 min read

Kids' Clothing Size Chart by Age and Height (Baby to Tween)

The labels say age. Kids don't grow on a schedule. Here's the full chart from 0 months to age 14 — height, weight, chest, waist — plus US/UK/EU/JP conversion and when to size up.

You buy a "12-month" outfit for your 11-month-old. It arrives. Your baby has already outgrown it.

Or the opposite. You order "size 8" for your 8-year-old. The shirt swallows him like a poncho. You wonder if you ordered wrong, or if your kid is unusually small.

Kids' clothing sizing is broken in a way adult sizing isn't. The labels say age. Kids don't grow on a schedule. A "size 6" can fit a 4-year-old who's tall or an 8-year-old who's small. The number on the label is a starting point, not a fact.

This guide gives you the complete kids' size chart from 0 months to age 14, the height and weight ranges that actually matter, the international comparison (US, UK, EU, JP), and the rule for when to size up so the clothes last more than a month. Includes a separate breakdown for babies, toddlers, and tweens.

How Kids' Clothing Sizes Actually Work

Kids' clothing uses three sizing systems based on age range.

Babies (0 to 24 months)

Sized in months: 0-3M, 3-6M, 6-9M, 9-12M, 12-18M, 18-24M. Each label has weight and height ranges, not a single age.

Toddlers (2T to 5T)

Sized in years with a "T" for toddler: 2T, 3T, 4T, 5T. Cut for diapered or post-diaper bodies, with snap-button accessibility. Size 5T overlaps with size 5 (non-toddler) but with a different cut.

Kids (4 to 16)

Sized in years: 4, 5, 6, 6X, 7, 8, 10, 12, 14, 16. Around size 7, brands split into separate boys' and girls' lines with different cuts.

The "T" matters

A 4T and a 4 are not interchangeable. 4T runs slightly bigger in the diaper area and has more accessibility features (snap-bottom, easy-on shoulders). Size 4 is cut for a kid who is potty-trained.

Baby Size Chart (0 to 24 Months)

Size	Age	Weight	Height
Newborn (NB)	0–1 month	up to 8 lbs / 3.5 kg	up to 21" / 53 cm
0–3M	0–3 months	8–12 lbs / 3.5–5.5 kg	21–24" / 53–61 cm
3–6M	3–6 months	12–16 lbs / 5.5–7.5 kg	24–26" / 61–66 cm
6–9M	6–9 months	16–20 lbs / 7.5–9 kg	26–28" / 66–71 cm
9–12M	9–12 months	20–24 lbs / 9–11 kg	28–30" / 71–76 cm
12–18M	12–18 months	22–27 lbs / 10–12 kg	30–32" / 76–81 cm
18–24M	18–24 months	25–29 lbs / 11.5–13 kg	32–34" / 81–86 cm

Always go by weight and height, not age

Babies grow at wildly different rates. A 6-month-old can wear anything from 3-6M to 12-18M depending on size.

Toddler Size Chart (2T to 5T)

Size	Age	Weight	Height
2T	2 years	27–31 lbs / 12–14 kg	33–36" / 84–91 cm
3T	3 years	30–34 lbs / 14–15.5 kg	36–39" / 91–99 cm
4T	4 years	34–39 lbs / 15.5–18 kg	39–42" / 99–107 cm
5T	5 years	39–43 lbs / 18–19.5 kg	42–45" / 107–114 cm

After age 5, sizing shifts from toddler (T) to kids' standard sizes (4, 5, 6, etc.). Some brands skip 5T and go directly from 4T to 5.

Kids' Size Chart (4 to 7)

Size	Age	Height	Weight	Chest	Waist
4	4 years	39–42" / 99–107 cm	35–40 lbs / 16–18 kg	22–23" / 56–58 cm	21–22" / 53–56 cm
5	5 years	42–45" / 107–114 cm	40–45 lbs / 18–20.5 kg	23–24" / 58–61 cm	21.5–22.5" / 55–57 cm
6	6 years	45–48" / 114–122 cm	45–50 lbs / 20.5–23 kg	24–25" / 61–64 cm	22–23" / 56–58 cm
6X (girls) / 7 (boys)	6–7 years	48–50" / 122–127 cm	50–55 lbs / 23–25 kg	25–26" / 64–66 cm	23–24" / 58–61 cm

Size 6X exists only for girls and is between 6 and 7. After 6X, girls' sizing jumps to 7.

Tween Size Chart — Boys (8 to 16)

By age 8, brands fully split into boys' and girls' lines. Cuts and proportions differ.

Size	Age	Height	Weight	Chest	Waist
8	7–8 years	50–52" / 127–132 cm	55–65 lbs / 25–29.5 kg	26–27" / 66–69 cm	24–25" / 61–64 cm
10	9–10 years	52–55" / 132–140 cm	65–78 lbs / 29.5–35.5 kg	27–28" / 69–71 cm	25–26" / 64–66 cm
12	11–12 years	55–58" / 140–147 cm	78–92 lbs / 35.5–42 kg	29–30" / 74–76 cm	26–27" / 66–69 cm
14	12–13 years	58–61" / 147–155 cm	92–105 lbs / 42–48 kg	30–32" / 76–81 cm	27–28" / 69–71 cm
16	13–14 years	61–64" / 155–163 cm	105–115 lbs / 48–52 kg	32–34" / 81–86 cm	28–29" / 71–74 cm

After size 16, most boys move into adult men's sizes (S or M).

Tween Size Chart — Girls (7 to 16)

Size	Age	Height	Weight	Chest	Waist	Hip
7	7 years	48–50" / 122–127 cm	50–55 lbs / 23–25 kg	25–26" / 64–66 cm	23–24" / 58–61 cm	26–27" / 66–69 cm
8	8 years	50–52" / 127–132 cm	55–65 lbs / 25–29.5 kg	26–27" / 66–69 cm	24–25" / 61–64 cm	27–28" / 69–71 cm
10	9–10 years	52–55" / 132–140 cm	65–78 lbs / 29.5–35.5 kg	28–29" / 71–74 cm	25–26" / 64–66 cm	29–30" / 74–76 cm
12	11–12 years	55–58" / 140–147 cm	78–92 lbs / 35.5–42 kg	30–31" / 76–79 cm	26–27" / 66–69 cm	31–32" / 79–81 cm
14	12–13 years	58–61" / 147–155 cm	92–105 lbs / 42–48 kg	32–33" / 81–84 cm	27–28" / 69–71 cm	33–34" / 84–86 cm
16	13–14 years	61–64" / 155–163 cm	105–115 lbs / 48–52 kg	33–35" / 84–89 cm	28–29" / 71–74 cm	35–36" / 89–91 cm

After size 16, most girls move into adult women's sizes (XS or S, roughly 0 to 4).

International Conversions

US, UK, EU, and Japanese kids' sizing all differ.

US Age	UK Age	EU Height (cm)	JP Height (cm)
0–3M	0–3M	56	60
3–6M	3–6M	62	70
6–9M	6–9M	68	70
12M	12M	74	80
18M	18M	80	80
24M / 2T	1.5–2 yrs	86	90
3T	2–3 yrs	92	100
4	3–4 yrs	98–104	110
5	4–5 yrs	110	110
6	5–6 yrs	116	120
7	6–7 yrs	122	130
8	7–8 yrs	128	130
10	9–10 yrs	140	140
12	11–12 yrs	152	150
14	13–14 yrs	164	160

EU and JP both use height in cm

European sizing by height is the most accurate system because kids vary so much in height for their age. Japanese sizing also uses height in cm and runs slightly larger numerically than EU at the same physical size.

UK age sizes match US age sizes closely but UK brands sometimes use additional inch ranges on the label.

Why Height Matters More Than Age

A 5-year-old can be 38 inches tall or 48 inches tall. A "size 5" label assumes 42 to 45 inches. If your child is on the short or tall end, the size 5 label fits like 3 or 7 respectively.

Always go by height first. The age on the label is a guideline for the average kid. Most kids are not average.

Measure your child's height standing flat against a wall

Shoes off, head against the wall, looking forward.

Match the height to the chart

US, EU, or JP, whichever the brand uses.

Pick the size that includes your child's height in its range

Confirm with weight as a secondary check.

Between two sizes? Size up

Kids grow. Sized-up clothes last 4 to 6 months instead of 4 to 6 weeks.

When to Size Up (and Three Exceptions)

Always size up by one when buying for kids, except in three cases.

Exception 1: Special occasion clothes

Weddings, holidays, photos. Match the chart precisely so the outfit fits on a specific date.

Exception 2: Safety items

Helmets, car seats, swim vests. Match the chart precisely. A loose helmet does not protect.

Exception 3: Flame-resistant pajamas

US: pajamas under size 14 must be tight-fitting by law. Match exactly.

For everyday clothes, the size-up rule means clothes last 4 to 6 months instead of 4 to 6 weeks.

Five Mistakes That Wreck Kids' Sizing

Going by age alone

Kids vary by 6+ inches at the same age. Use height first.

Forgetting about T sizes

A 4T and a size 4 are not the same. T sizes are cut for toddlers in or just out of diapers.

Not accounting for growth spurts

Kids grow 2 to 4 inches per year on average. Buy with growth allowance.

Ignoring international charts

EU 116 is not the same as US 116 (which doesn't exist). EU uses height in cm. US uses age in years. Convert before ordering.

Buying tight clothes for active kids

Kids climb, run, and stretch. Tight cuts tear at the seams within weeks. Size up.

FAQs

My kid is in between two sizes. What do I do?

Size up. Kids grow into clothes faster than they grow out of them with a small allowance.

Why does my kid wear different sizes at different brands?

Brands cut sizes differently. Mass-market brands (Old Navy, Gap, Carter's) tend to run roomier. Designer kids' brands run smaller and closer to listed dimensions.

Are 4T and 4 the same size?

No. 4T is cut wider in the diaper area and has snap closures or accessibility features. Size 4 is cut for a fully potty-trained kid.

My 9-year-old is a kids' 14. What size do I order in adult?

Roughly women's XS or S, men's XS, depending on body. Re-measure chest and waist before buying adult sizes; the cut is different.

How often should I re-measure my child?

Every 3 months until age 4, every 6 months from 4 to 12, then yearly until adulthood.

Should I go by age or height when picking a kids' size?

Height. Kids vary by 6+ inches at the same age. The age on a size label assumes an average kid — most kids are not average. Measure standing height and match it to the chart.

Save the Numbers and Update Them

Unlike adult sizing, kids' measurements change constantly.

Add to a phone note for each child:

Height (inches and cm)
Weight
Chest, waist, hip
Inseam
Foot length
Last measured date

Update every 3 to 6 months. The next time you shop online, you have the right numbers ready and you stop ordering by age guess. Stores running Tailor Size Guide let parents save these numbers per child and reuse them across every product.

Selling kids' or family apparel on Shopify?

Sizing returns are amplified in kids' clothing because parents can't predict growth. Tailor Size Guide adds height and age-based size charts and recommendation engines to your product pages so parents pick the right size with confidence.

Install the Shopify app Read the docs