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Baby sizing, brand by brand · Little & Youth

What size is 0–3M?How a 0–3M compares across 36 baby brands — by weight

A 0–3M isn't the same everywhere. Baby sizes are set mostly by weight, and each brand draws its 0–3M a little differently. Here is every brand on Little & Youth that sells a 0–3M, then the brands that call the same weight something else.

The short answer: At the 36 brands on Little & Youth that sell a size called 0–3M, it fits a baby of about 8–12 lb, roughly 20.8–24 in long — the middle of those brands' own published ranges. Baby sizes are set mostly by weight, then length, so weigh before you buy. Across those brands the same 0–3M spans 6.5–15 lb. 11 more brands sell a size with a different name whose own published weight overlaps this range; they're listed separately, exactly as each brand prints them.

Brands that sell a size called 0–3M

Each brand's own published weight and length for its 0–3M, lightest to heaviest. Expand "source" for the chart each row comes from.

0–3M across 36 brands — weight (lb) and length (in), as each brand publishes them.
BrandTheir sizeWeightLength
Uniqlo Kids0-3 months(50)6.6 lb17.72–21.65 in
source
Chart: BABY Nude Dimensions · Source: https://www.uniqlo.com/us/en/size/dimension_kids.html · Captured: 2026-09-04
Tea Collection0-3M8–11 lb20–24 in
source
Chart: Newborn Nb To 6-12m · Source: https://teacollection.com/pages/size-chart · Captured: 2026-09-09
babyGap0 - 3 mos7–12 lb18–23 in
source
Chart: BABY SIZE CHART · Source: https://www.gap.com/customer-service/size-charts?cid=2105 · Captured: 2026-09-04
Calvin Klein Kids0/3 Months girls8–12 lb22–24 in
source
Chart: Infant Girls · Source: https://www.calvinklein.us/en/kids-size-guide.html · Captured: 2026-09-09
Calvin Klein Kids0/3 Months boys8–12 lb22–24 in
source
Chart: Infant Boys · Source: https://www.calvinklein.us/en/kids-size-guide.html · Captured: 2026-09-09
Cloud Island0-3M9–12 lb20.5–23.5 in
source
Chart: Baby · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cloud-island/regular.html · Captured: 2026-10-05
Garanimals0-3M6.5–12 lb20.5–23 in
source
Source: https://www.garanimals.com/size-chart · Captured: 2026-09-04
Gerber Childrenswear0-3M8–12 lb21–24 in
source
Chart: Preemie to Toddler · Source: https://www.gerberchildrenswear.com/pages/size-chart-gerber-childrenswear · Captured: 2026-09-04
Guess0/3Mup to 12 lbup to 23.5 in
source
Source: https://content.guess.com/GuessUS/Frontend/sizechart/kids_sizecharts.html · Captured: 2026-09-04
Hanna Andersson0-3M (50 cm)8–12 lb18–22 in
source
Chart: Baby & Toddler · Source: https://www.hannaandersson.com/kids-size-chart.html · Captured: 2026-09-04
Hatley0-3m7–12 lb18–22.75 in
source
Chart: Baby · Source: https://us.hatley.com/pages/size-chart · Captured: 2026-10-05
Janie and Jack0 - 3 m8–12 lb19–23 in
source
Chart: Baby - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Kyte Baby0-3M9–12 lb21–23 in
source
Chart: Infant & Toddler apparel (weight+height) · Source: https://kytebaby.com/pages/sizing-chart · Captured: 2026-09-30
Little Sleepies0-3m8–12 lb21–23 in
source
Source: https://littlesleepies.com/pages/sizing-guide · Captured: 2026-10-07
Macy's First Impressions0-3Mup to 12 lbup to 23.5 in
source
Chart: Baby · Source: https://www.macys.com/xapi/digital/v1/product/21640640/sizechart/267301644?clientId=PROS · Captured: 2026-09-20
Magnetic Me0-3M8–12 lb21.5–23 in
source
Chart: Baby · Source: https://www.magneticme.com/pages/size-chart · Captured: 2026-09-04
Monica + Andy0-3M9–12 lb18–23 in
source
Chart: Baby Sizes · Source: https://monicaandandy.com/products/oversized-slouchy-tee · Captured: 2026-10-05
Target Cat & Jack0-3M9–12 lb20.5–23.5 in
source
Chart: Baby · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cat-jack/regular.html · Captured: 2026-09-20
Under Armour Kids0-3M8–12 lb20.5–24 in
source
Chart: Infant · Source: https://www.underarmour.com/en-us/t/size-guide/boys-tops/ · Captured: 2026-09-20
Walmart Wonder Nation0-3M6.5–12 lb20.5–23 in
source
Source: https://www.walmart.com/ip/Wonder-Nation-Boys-Kid-Tough-T-Shirt-Sizes-XS-XXL-and-Husky/938545778 · Captured: 2026-09-20
Hudson Baby0-3M9–12.5 lb21.5–24 in
source
Chart: Baby Clothing · Source: https://hudsonchildrenswear.com/pages/sizechart.html · Captured: 2026-10-05
Levi's Kids0/3M7–12.5 lb20.5–24 in
source
Chart: Kids Baby - NEWBORN · Source: https://www.levi.com/US/en_US/info/sizeguide · Captured: 2026-09-04
JoJo Maman Bébé0-3 mths12.8 lb24.41 in
source
Chart: Baby 0 - 24 Months · Source: https://www.jojomamanbebe.com/us/en/sizing-and-care-guide/baby-and-childrens-size-guide · Captured: 2026-09-04
Mini Boden0-3Mup to 13 lbup to 24.5 in
source
Chart: GIRLS & BOYS BODY MEASUREMENTS · Source: https://global.boden.com/pages/childrens-size-and-fit-chart · Captured: 2026-09-04
Quincy Mae0-3m8–13 lb21–24 in
source
Chart: Quincy Mae — Body · Source: https://ryleecru.customerdesk.io/#rp-customer-widget-faq-ebe725ad-f773-4634-bbd6-0c8dd0af7e18 · Captured: 2026-09-13
Rylee + Cru0-3m8–13 lb21–24 in
source
Chart: Rylee + Cru — Body (Baby + Kids) · Source: https://ryleecru.customerdesk.io/#rp-customer-widget-faq-ebe725ad-f773-4634-bbd6-0c8dd0af7e18 · Captured: 2026-09-13
Primark Kids0-3 months13.2 lb22.05–24.41 in
source
Chart: Baby Clothes: Newborn - 36 Months (product-page Size Guide) · Source: https://www.primark.com/en-us/p/0-18mths-disney-pixars-toy-story-newborn-romper-ivory-991181820006 · Captured: 2026-10-07
Columbia Kids0-3M14 lb22.5 in
source
Chart: Infant · Source: https://www.columbia.com/t/size-fit/ · Captured: 2026-09-19
Gymboree0-3M10–14 lb20.5–24 in
source
Chart: Baby · Source: https://www.gymboree.com/us/content/size-chart · Captured: 2026-10-07
J.Crew Crewcuts0 - 3 M7–14 lb20.5–24 in
source
Chart: Baby (Height/Weight/Waist/Chest; no metric table published) · Source: https://www.jcrew.com/r/size-charts · Captured: 2026-09-04
Old Navy0-3M7–14 lb21.5–24 in
source
Chart: Baby · Source: https://oldnavy.gap.com/browse/product.do?pid=614457002 · Captured: 2026-09-20
The Children's Place0-3M10–14 lb20.5–24 in
source
Source: https://www.childrensplace.com/us/content/size-chart · Captured: 2026-10-07
Joules Kids0-3m Up to 3m9.9–14.1 lb22–24.5 in
source
Chart: BABY & TODDLER · Source: https://joulesuk.zendesk.com/hc/en-gb/articles/30459306847505-Size-Guides · Captured: 2026-09-04
Patagonia Kids0-3M7–15 lb21–24 in
source
Chart: Infants & Toddlers Size Chart · Source: https://www.patagonia.com/size-unisex-infant-data.html?format=ajax · Captured: 2026-09-04
The North Face Kids0M-3M10–15 lb22–25 in
source
Chart: Baby Apparel · Source: https://www.thenorthface.com/en-us/help/size-charts · Captured: 2026-09-09
Adidas Kids0-3M—20–22 in
source
Chart: Babies & toddlers (age 0-3 years) · Source: https://www.adidas.com/us/help/size_charts/kids-clothing · Captured: 2026-09-20
Puma Kids0/3M boys—22–24 in
source
Chart: Boys - Infant + Toddler Clothing · Source: https://us.puma.com/api/graphql · Captured: 2026-09-20
Puma Kids0/3M girls—22–24 in
source
Chart: Girls - Infant + Toddler Clothing · Source: https://us.puma.com/api/graphql · Captured: 2026-09-20

Same weight, different label

These brands don't sell a size called 0–3M. Each row is one of the brand's own sizes whose published weight overlaps 8–12 lb — shown with the brand's label, weight and length as printed. Labels are the brands' own; we don't treat them as the same size as 0–3M.

Other baby sizes whose own published weight overlaps the 0–3M weight band.
BrandTheir sizeWeightLength
Converse Kids0 Months6–9.5 lb20–22 in
source
Chart: Infant & Toddler Apparel · Source: https://www.converse.com/size-chart-guide?id=infantandtoddler-tops&modal=false · Captured: 2026-09-09
Jacadi1M6–10 lb21 in
source
Chart: Baby · Source: https://www.jacadi.us/size-chart · Captured: 2026-09-20
Polo Ralph Lauren KidsNBup to 10 lbup to 21 in
source
Chart: Baby Size Guide - Apparel · Source: https://www.ralphlauren.com/baby-size-guide/baby_all_ages_apparel.html · Captured: 2026-09-09
BoxLunch3 Months8–12 lb21–24 in
source
Chart: Infant/Baby · Source: https://www.boxlunch.com/customer-service/merchandise/size-fit-guide/ · Captured: 2026-09-04
Primary0-39–12 lb18–23 in
source
Chart: All Baby Clothing (rows 2 and 3 omitted - see notes.md) · Source: https://size-chart-server.primary.codes/all-baby-clothing · Captured: 2026-09-09
Amazon Essentials Kids3M8–12.5 lb20–23.5 in
source
Source: https://z-ecx.images-amazon.com/images/G/01/apparel/en_US/html/sizechart/kids._V201566742_.html · Captured: 2026-09-20
Burt's Bees Baby3M9–12.5 lb21.5–24 in
source
Chart: Baby/Toddler/Kids · Source: https://www.burtsbeesbaby.com/pages/baby-clothes-size-chart · Captured: 2026-09-04
Carter's3M9–12.5 lb21.5–24 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 7–13 lb, 21–23.5 in
Little Planet by Carter's3M9–12.5 lb21.5–24 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 7–13 lb, 21–23.5 in
OshKosh B'gosh3M9–12.5 lb21.5–24 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 7–13 lb, 21–23.5 in
abercrombie kids3 mos9.5–13 lb22–25 in
source
Chart: Baby & Toddler · Source: https://www.abercrombie.com/shop/us/kids/p/straight-jeans-56562026 · Captured: 2026-09-04
Jacadi3M9–13 lb24 in
source
Chart: Baby · Source: https://www.jacadi.us/size-chart · Captured: 2026-09-20
Polo Ralph Lauren Kids3M10–14 lb21–24 in
source
Chart: Baby Size Guide - Apparel · Source: https://www.ralphlauren.com/baby-size-guide/baby_all_ages_apparel.html · Captured: 2026-09-09
Converse Kids3 Months10–14.5 lb22–24.5 in
source
Chart: Infant & Toddler Apparel · Source: https://www.converse.com/size-chart-guide?id=infantandtoddler-tops&modal=false · Captured: 2026-09-09

Weight, length and the diaper

Two babies of the same age can be two sizes apart, which is why the age on the tag is the weakest guide. Go by weight first, then length. Bodysuits and footed sleepers also have to close over a diaper: if your baby is near the top of a brand's range, is long for their weight, or wears cloth diapers, the next size up usually snaps more easily.

Common questions about 0–3 months sizes

What weight is a 0–3M for?

At the 36 brands on Little & Youth that sell a 0–3M, it fits a baby of about 8–12 lb — the middle of their own published ranges. Brands vary: the same 0–3M spans 6.5–15 lb across them, so check the brand's own weight range.

Is a 0–3M the same at every brand?

No. Baby sizes aren't standardized — across the brands here a 0–3M covers 6.5–15 lb, and some brands name the same weight differently (a single age like 6M, months like 6 mos, or a centimetre size). Weigh and measure your baby and compare against each brand's own chart.

Know your baby's size at every brand. Let Little & Youth do it.

Enter your baby's weight and length once and Little & Youth shows the size to buy across the brands on the site — each from that brand's own published chart.

Find your child's size →
Their Measurements. Right Size. Brand by Brand.
How we know this is accurate. Every weight and length on this page is transcribed from that brand's own published baby size chart — no estimates and no averaged-out "standard". Where a brand prints only an upper limit ("up to 7 lb"), that is how it is shown. Brands update their charts, so confirm against the brand's live chart before you buy. Little & Youth is independent and not affiliated with any brand listed. Figures verified 2026-10-08.