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Baby sizing, brand by brand · Little & Youth

What size is 3–6M?How a 3–6M compares across 37 baby brands — by weight

A 3–6M isn't the same everywhere. Baby sizes are set mostly by weight, and each brand draws its 3–6M a little differently. Here is every brand on Little & Youth that sells a 3–6M, then the brands that call the same weight something else.

The short answer: At the 37 brands on Little & Youth that sell a size called 3–6M, it fits a baby of about 12.5–17 lb, roughly 24–26.5 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 3–6M spans 11–20 lb. 12 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 3–6M

Each brand's own published weight and length for its 3–6M, lightest to heaviest. Expand "source" for the chart each row comes from.

3–6M across 37 brands — weight (lb) and length (in), as each brand publishes them.
BrandTheir sizeWeightLength
Uniqlo Kids3-6 months(60)13.2 lb21.65–25.59 in
source
Chart: BABY Nude Dimensions · Source: https://www.uniqlo.com/us/en/size/dimension_kids.html · Captured: 2026-09-04
Tea Collection3-6M11–15 lb24–27 in
source
Chart: Newborn Nb To 6-12m · Source: https://teacollection.com/pages/size-chart · Captured: 2026-09-09
Calvin Klein Kids3/6 Months girls12–16 lb24–26 in
source
Chart: Infant Girls · Source: https://www.calvinklein.us/en/kids-size-guide.html · Captured: 2026-09-09
Calvin Klein Kids3/6 Months boys12–16 lb24–26 in
source
Chart: Infant Boys · Source: https://www.calvinklein.us/en/kids-size-guide.html · Captured: 2026-09-09
Cloud Island3-6M12.5–16 lb24–25.5 in
source
Chart: Baby · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cloud-island/regular.html · Captured: 2026-10-05
Garanimals3-6M12.5–16 lb23.5–26 in
source
Source: https://www.garanimals.com/size-chart · Captured: 2026-09-04
Gerber Childrenswear3-6M12–16 lb24–26 in
source
Chart: Preemie to Toddler · Source: https://www.gerberchildrenswear.com/pages/size-chart-gerber-childrenswear · Captured: 2026-09-04
Hanna Andersson3-6M (60 cm)12–16 lb22–26 in
source
Chart: Baby & Toddler · Source: https://www.hannaandersson.com/kids-size-chart.html · Captured: 2026-09-04
Hatley3-6m12–16 lb22.75–26.75 in
source
Chart: Baby · Source: https://us.hatley.com/pages/size-chart · Captured: 2026-10-05
Magnetic Me3-6M12–16 lb23.5–26 in
source
Chart: Baby · Source: https://www.magneticme.com/pages/size-chart · Captured: 2026-09-04
Monica + Andy3-6M12–16 lb23–26 in
source
Chart: Baby Sizes · Source: https://monicaandandy.com/products/oversized-slouchy-tee · Captured: 2026-10-05
Target Cat & Jack3-6M12.5–16 lb24–25.5 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 Kids3-6M12–16 lb24–27 in
source
Chart: Infant · Source: https://www.underarmour.com/en-us/t/size-guide/boys-tops/ · Captured: 2026-09-20
Walmart Wonder Nation3-6M12.5–16 lb23.5–26 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
Guess3/6M12.5–16.5 lb24–26.5 in
source
Source: https://content.guess.com/GuessUS/Frontend/sizechart/kids_sizecharts.html · Captured: 2026-09-04
Levi's Kids3/6M12.5–16.5 lb24–26.5 in
source
Chart: Kids Baby - NEWBORN · Source: https://www.levi.com/US/en_US/info/sizeguide · Captured: 2026-09-04
babyGap3 - 6 mos12–17 lb23–27 in
source
Chart: BABY SIZE CHART · Source: https://www.gap.com/customer-service/size-charts?cid=2105 · Captured: 2026-09-04
Hudson Baby3-6M12.5–17 lb24–27 in
source
Chart: Baby Clothing · Source: https://hudsonchildrenswear.com/pages/sizechart.html · Captured: 2026-10-05
Janie and Jack3 - 6 m girls12–17 lb23–25 in
source
Chart: Baby Girl - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Janie and Jack3 - 6 m boys12–17 lb23–25 in
source
Chart: Baby Boy - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Janie and Jack3 - 6 m12–17 lb23–25 in
source
Chart: Baby - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Kyte Baby3-6M12–17 lb23–27 in
source
Chart: Infant & Toddler apparel (weight+height) · Source: https://kytebaby.com/pages/sizing-chart · Captured: 2026-09-30
Little Sleepies3-6m12–17 lb23–27 in
source
Source: https://littlesleepies.com/pages/sizing-guide · Captured: 2026-10-07
Macy's First Impressions3-6M12–17 lb23.5–26.5 in
source
Chart: Baby · Source: https://www.macys.com/xapi/digital/v1/product/21640640/sizechart/267301644?clientId=PROS · Captured: 2026-09-20
Old Navy3-6M14–17 lb24–26.5 in
source
Chart: Baby · Source: https://oldnavy.gap.com/browse/product.do?pid=614457002 · Captured: 2026-09-20
Mini Boden3-6Mup to 17.5 lbup to 27 in
source
Chart: GIRLS & BOYS BODY MEASUREMENTS · Source: https://global.boden.com/pages/childrens-size-and-fit-chart · Captured: 2026-09-04
JoJo Maman Bébé3-6 mths17.6 lb26.77 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
Primark Kids3-6 months17.6 lb24.41–26.77 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 Kids3-6M18 lb25.5 in
source
Chart: Infant · Source: https://www.columbia.com/t/size-fit/ · Captured: 2026-09-19
Gymboree3-6M14–18 lb24–27 in
source
Chart: Baby · Source: https://www.gymboree.com/us/content/size-chart · Captured: 2026-10-07
J.Crew Crewcuts3 - 6 M14–18 lb24–27 in
source
Chart: Baby (Height/Weight/Waist/Chest; no metric table published) · Source: https://www.jcrew.com/r/size-charts · Captured: 2026-09-04
Quincy Mae3-6m14–18 lb24–27 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 + Cru3-6m14–18 lb24–27 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
The Children's Place3-6M14–18 lb24–27 in
source
Source: https://www.childrensplace.com/us/content/size-chart · Captured: 2026-10-07
Joules Kids3-6m14.1–18.1 lb24.5–27 in
source
Chart: BABY & TODDLER · Source: https://joulesuk.zendesk.com/hc/en-gb/articles/30459306847505-Size-Guides · Captured: 2026-09-04
Patagonia Kids3-6M15–20 lb25–27 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 Kids3M-6M15–20 lb25–28 in
source
Chart: Baby Apparel · Source: https://www.thenorthface.com/en-us/help/size-charts · Captured: 2026-09-09
Mango Kids3-6 months—26.77 in
source
Chart: Newborn — full body ladder (as published under "Pajamas") · Source: https://shop.mango.com/us/en/size-guide · Captured: 2026-09-20
Puma Kids3/6M boys—24–27 in
source
Chart: Boys - Infant + Toddler Clothing · Source: https://us.puma.com/api/graphql · Captured: 2026-09-20
Puma Kids3/6M girls—24–27 in
source
Chart: Girls - Infant + Toddler Clothing · Source: https://us.puma.com/api/graphql · Captured: 2026-09-20
Zara Kids3-6 months—up to 26.77 in
source
Chart: Baby · Source: https://www.zara.com/us/en/textured-floral-print-bodysuit-p05767587.html · Captured: 2026-09-20

Same weight, different label

These brands don't sell a size called 3–6M. Each row is one of the brand's own sizes whose published weight overlaps 12.5–17 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 3–6M.

Other baby sizes whose own published weight overlaps the 3–6M weight band.
BrandTheir sizeWeightLength
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
Primary3-612–15 lb23–25 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
BoxLunch6 Months12–16 lb24–26 in
source
Chart: Infant/Baby · Source: https://www.boxlunch.com/customer-service/merchandise/size-fit-guide/ · Captured: 2026-09-04
Amazon Essentials Kids6M13–16.5 lb24–25.5 in
source
Source: https://z-ecx.images-amazon.com/images/G/01/apparel/en_US/html/sizechart/kids._V201566742_.html · Captured: 2026-09-20
abercrombie kids6 mos13–17 lb25–27 in
source
Chart: Baby & Toddler · Source: https://www.abercrombie.com/shop/us/kids/p/straight-jeans-56562026 · Captured: 2026-09-04
Burt's Bees Baby6M12.5–17 lb24–26.5 in
source
Chart: Baby/Toddler/Kids · Source: https://www.burtsbeesbaby.com/pages/baby-clothes-size-chart · Captured: 2026-09-04
Carter's6M12.5–17 lb24–27 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 13–17 lb, 23.5–26 in
Little Planet by Carter's6M12.5–17 lb24–27 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 13–17 lb, 23.5–26 in
OshKosh B'gosh6M12.5–17 lb24–27 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 13–17 lb, 23.5–26 in
Converse Kids6 Months15–18 lb24.5–26.5 in
source
Chart: Infant & Toddler Apparel · Source: https://www.converse.com/size-chart-guide?id=infantandtoddler-tops&modal=false · Captured: 2026-09-09
Jacadi6M13–18 lb26 in
source
Chart: Baby · Source: https://www.jacadi.us/size-chart · Captured: 2026-09-20
Noralee3m14–18 lb24–27 in
source
Chart: Noralee — Body · Source: https://ryleecru.customerdesk.io/#rp-customer-widget-faq-ebe725ad-f773-4634-bbd6-0c8dd0af7e18 · Captured: 2026-09-13
Primary6-915–18 lb25–27 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
Polo Ralph Lauren Kids6M14.5–18.5 lb24.5–27 in
source
Chart: Baby Size Guide - Apparel · Source: https://www.ralphlauren.com/baby-size-guide/baby_all_ages_apparel.html · Captured: 2026-09-09
Primary6-1215–22 lb25–29 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

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 3–6 months sizes

What weight is a 3–6M for?

At the 37 brands on Little & Youth that sell a 3–6M, it fits a baby of about 12.5–17 lb — the middle of their own published ranges. Brands vary: the same 3–6M spans 11–20 lb across them, so check the brand's own weight range.

Is a 3–6M the same at every brand?

No. Baby sizes aren't standardized — across the brands here a 3–6M covers 11–20 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.