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Baby sizing, brand by brand · Little & Youth

What size is 9–12M?How a 9–12M compares across 15 baby brands — by weight

A 9–12M isn't the same everywhere. Baby sizes are set mostly by weight, and each brand draws its 9–12M a little differently. Here is every brand on Little & Youth that sells a 9–12M, then the brands that call the same weight something else.

The short answer: At the 15 brands on Little & Youth that sell a size called 9–12M, it fits a baby of about 21–24 lb, roughly 29–30.5 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 9–12M spans 18–26 lb. 34 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 9–12M

Each brand's own published weight and length for its 9–12M, lightest to heaviest. Expand "source" for the chart each row comes from.

9–12M across 15 brands — weight (lb) and length (in), as each brand publishes them.
BrandTheir sizeWeightLength
JoJo Maman Bébé9-12 mths22 lb31.5 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
Magnetic Me9-12M19–22 lb28.5–30 in
source
Chart: Baby · Source: https://www.magneticme.com/pages/size-chart · Captured: 2026-09-04
Tea Collection9-12M18–22 lb29–30.5 in
source
Chart: Newborn Nb To 6-12m · Source: https://teacollection.com/pages/size-chart · Captured: 2026-09-09
Cloud Island9-12M20–23 lb28–30.5 in
source
Chart: Baby · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cloud-island/regular.html · Captured: 2026-10-05
Joules Kids9-12m20.9–24 lb29–31.5 in
source
Chart: BABY & TODDLER · Source: https://joulesuk.zendesk.com/hc/en-gb/articles/30459306847505-Size-Guides · Captured: 2026-09-04
Mini Boden9-12Mup to 24 lbup to 31.5 in
source
Chart: GIRLS & BOYS BODY MEASUREMENTS · Source: https://global.boden.com/pages/childrens-size-and-fit-chart · Captured: 2026-09-04
Monica + Andy9-12M20–24 lb28–30 in
source
Chart: Baby Sizes · Source: https://monicaandandy.com/products/oversized-slouchy-tee · Captured: 2026-10-05
Primark Kids9-12 months24.3 lb29.13–31.5 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
Hatley9-12m21–25 lb28–29.25 in
source
Chart: Baby · Source: https://us.hatley.com/pages/size-chart · Captured: 2026-10-05
Hudson Baby9-12M21–25 lb28.5–30 in
source
Chart: Baby Clothing · Source: https://hudsonchildrenswear.com/pages/sizechart.html · Captured: 2026-10-05
Gymboree9-12M22–26 lb29–30.5 in
source
Chart: Baby · Source: https://www.gymboree.com/us/content/size-chart · Captured: 2026-10-07
J.Crew Crewcuts9 - 12 M22–26 lb29–30.5 in
source
Chart: Baby (Height/Weight/Waist/Chest; no metric table published) · Source: https://www.jcrew.com/r/size-charts · Captured: 2026-09-04
The Children's Place9-12M22–26 lb29–30.5 in
source
Source: https://www.childrensplace.com/us/content/size-chart · Captured: 2026-10-07
Joules Kids9-12 mths girls—31.5 in
source
Chart: GIRLS CLOTHING · Source: https://joulesuk.zendesk.com/hc/en-gb/articles/30459306847505-Size-Guides · Captured: 2026-09-04
Joules Kids9-12 mths boys—31.5 in
source
Chart: BOYS CLOTHING · Source: https://joulesuk.zendesk.com/hc/en-gb/articles/30459306847505-Size-Guides · Captured: 2026-09-04
Mango Kids9-12 months—31.5 in
source
Chart: Newborn — full body ladder (as published under "Pajamas") · Source: https://shop.mango.com/us/en/size-guide · Captured: 2026-09-20
Mango Kids9-12 months girls—31.5 in
source
Chart: Baby girl — full body ladder (as published under "Dresses and jumpsuits") [4 years / 5-6 years omitted - identical rows live on the Girl/Boy chart] · Source: https://shop.mango.com/us/en/size-guide · Captured: 2026-09-20
Mango Kids9-12 months boys—31.5 in
source
Chart: Baby boy — full body ladder (as published under "Sweatshirts") [4 years / 5-6 years omitted - identical rows live on the Girl/Boy chart] · Source: https://shop.mango.com/us/en/size-guide · Captured: 2026-09-20
Zara Kids9-12 months—up to 31.5 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 9–12M. Each row is one of the brand's own sizes whose published weight overlaps 21–24 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 9–12M.

Other baby sizes whose own published weight overlaps the 9–12M weight band.
BrandTheir sizeWeightLength
babyGap6 - 12 mos20–22 lb28–29 in
source
Chart: BABY SIZE CHART · Source: https://www.gap.com/customer-service/size-charts?cid=2105 · Captured: 2026-09-04
Garanimals12M19.5–22 lb28–29.5 in
source
Source: https://www.garanimals.com/size-chart · Captured: 2026-09-04
Walmart Wonder Nation12M19.5–22 lb28–29.5 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
Little Sleepies6-12m17–23 lb27–31 in
source
Source: https://littlesleepies.com/pages/sizing-guide · Captured: 2026-10-07
Target Cat & Jack12M20–23 lb28–30.5 in
source
Chart: Baby · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cat-jack/regular.html · Captured: 2026-09-20
Target Cat & Jack12M girls20–23 lb28–30.5 in
source
Chart: Toddler Girls · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cat-jack/toddler-girls.html · Captured: 2026-09-04
Target Cat & Jack12M boys20–23 lb28–30.5 in
source
Chart: Toddler Boys · Source: https://digitalcontent.target.com/itemcontent/sizecharts/htmlfragments/baby-toddler-clothing/cat-jack/regular.html · Captured: 2026-09-20
Amazon Essentials Kids12M21–23.5 lb28–30.5 in
source
Source: https://z-ecx.images-amazon.com/images/G/01/apparel/en_US/html/sizechart/kids._V201566742_.html · Captured: 2026-09-20
BoxLunch12 Months20–24 lb28–30 in
source
Chart: Infant/Baby · Source: https://www.boxlunch.com/customer-service/merchandise/size-fit-guide/ · Captured: 2026-09-04
Gerber Childrenswear12M20–24 lb28–30 in
source
Chart: Preemie to Toddler · Source: https://www.gerberchildrenswear.com/pages/size-chart-gerber-childrenswear · Captured: 2026-09-04
Cotton Pajamas chart, same size: 16–20 lb, 27–30 in
Guess12M20.5–24 lb29–30.5 in
source
Source: https://content.guess.com/GuessUS/Frontend/sizechart/kids_sizecharts.html · Captured: 2026-09-04
Hanna Andersson12-18M (75 cm)20–24 lb28–30 in
source
Chart: Baby & Toddler · Source: https://www.hannaandersson.com/kids-size-chart.html · Captured: 2026-09-04
Old Navy12-18M21–24 lb29–31.5 in
source
Chart: Baby · Source: https://oldnavy.gap.com/browse/product.do?pid=614457002 · Captured: 2026-09-20
Levi's Kids12M20.5–24.5 lb28.5–30.5 in
source
Chart: Kids Baby - INFANT · Source: https://www.levi.com/US/en_US/info/sizeguide · Captured: 2026-09-04
abercrombie kids12 mos21–25 lb29–31 in
source
Chart: Baby & Toddler · Source: https://www.abercrombie.com/shop/us/kids/p/straight-jeans-56562026 · Captured: 2026-09-04
Burt's Bees Baby12M21–25 lb28.5–30.5 in
source
Chart: Baby/Toddler/Kids · Source: https://www.burtsbeesbaby.com/pages/baby-clothes-size-chart · Captured: 2026-09-04
Carter's12M21–25 lb28.5–30 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 21–24.5 lb, 28–30 in
Converse Kids12 Months22.5–25 lb29–31.5 in
source
Chart: Infant & Toddler Apparel · Source: https://www.converse.com/size-chart-guide?id=infantandtoddler-tops&modal=false · Captured: 2026-09-09
Jacadi18M22–25 lb32 in
source
Chart: Baby · Source: https://www.jacadi.us/size-chart · Captured: 2026-09-20
Kyte Baby12-18M22–25 lb29–31 in
source
Chart: Infant & Toddler apparel (weight+height) · Source: https://kytebaby.com/pages/sizing-chart · Captured: 2026-09-30
L.L. Bean Kids12-18 Months22–25 lb29–32 in
source
Chart: Kids Sizing - Infants · Source: https://www.llbean.com/llb/shop/518113?page=sizing-charts · Captured: 2026-09-04
Little Planet by Carter's12M21–25 lb28.5–30 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 21–24.5 lb, 28–30 in
Macy's Epic Threads12M22–25 lb28–30 in
source
Source: https://www.macys.com/xapi/digital/v1/product/18446918/sizechart/241466560?clientId=PROS · Captured: 2026-09-09
Macy's First Impressions12M22–25 lb28–30 in
source
Chart: Baby · Source: https://www.macys.com/xapi/digital/v1/product/21640640/sizechart/267301644?clientId=PROS · Captured: 2026-09-20
OshKosh B'gosh12M21–25 lb28.5–30 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 21–24.5 lb, 28–30 in
Otter Avenue12M21–25 lb28.5–30 in
source
Chart: Pajamas (general body ladder) · Source: https://www.carters.com/size-chart · Captured: 2026-10-07
Outerwear chart, same size: 21–24.5 lb, 28–30 in
Patagonia Kids6-12M20–25 lb28–31 in
source
Chart: Infants & Toddlers Size Chart · Source: https://www.patagonia.com/size-unisex-infant-data.html?format=ajax · Captured: 2026-09-04
Polo Ralph Lauren Kids12M22.5–25 lb29.5–31 in
source
Chart: Baby Size Guide - Apparel · Source: https://www.ralphlauren.com/baby-size-guide/baby_all_ages_apparel.html · Captured: 2026-09-09
The North Face Kids6M-12M20–25 lb28–31 in
source
Chart: Baby Apparel · Source: https://www.thenorthface.com/en-us/help/size-charts · Captured: 2026-09-09
Calvin Klein Kids18 Months girls22–26 lb30–32 in
source
Chart: Infant Girls · Source: https://www.calvinklein.us/en/kids-size-guide.html · Captured: 2026-09-09
Calvin Klein Kids18 Months boys22–26 lb30–32 in
source
Chart: Infant Boys · Source: https://www.calvinklein.us/en/kids-size-guide.html · Captured: 2026-09-09
Garanimals18M22.5–26 lb30–31.5 in
source
Source: https://www.garanimals.com/size-chart · Captured: 2026-09-04
Quincy Mae12-18m22–26 lb30–33 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 + Cru12-18m22–26 lb30–33 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
Under Armour Kids18M22–26 lb30.5–33 in
source
Chart: Infant · Source: https://www.underarmour.com/en-us/t/size-guide/boys-tops/ · Captured: 2026-09-20
Walmart Wonder Nation18M22.5–26 lb30–31.5 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
babyGap12 - 18 mos22–27 lb29–31 in
source
Chart: BABY SIZE CHART · Source: https://www.gap.com/customer-service/size-charts?cid=2105 · Captured: 2026-09-04
Janie and Jack12 - 18 m girls22–27 lb29–31 in
source
Chart: Baby Girl - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Janie and Jack12 - 18 m boys22–27 lb29–31 in
source
Chart: Baby Boy - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Janie and Jack12 - 18 m22–27 lb29–31 in
source
Chart: Baby - Clothing · Source: https://www.janieandjack.com/janieandjack-size-charts.html?lang=en_US · Captured: 2026-09-04
Primary12-1822–27 lb29–31 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
Noralee12m22–28 lb30–33 in
source
Chart: Noralee — Body · Source: https://ryleecru.customerdesk.io/#rp-customer-widget-faq-ebe725ad-f773-4634-bbd6-0c8dd0af7e18 · Captured: 2026-09-13

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 9–12 months sizes

What weight is a 9–12M for?

At the 15 brands on Little & Youth that sell a 9–12M, it fits a baby of about 21–24 lb — the middle of their own published ranges. Brands vary: the same 9–12M spans 18–26 lb across them, so check the brand's own weight range.

Is a 9–12M the same at every brand?

No. Baby sizes aren't standardized — across the brands here a 9–12M covers 18–26 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.