Japanese Diaper Sizes and Brands: How to Read the Pack and Where to Buy

You’ve counted the diapers in the suitcase three times and it’s still not enough for two weeks. Or you’re standing in front of a wall of Japanese packs, every one with a cartoon baby on it, and none of the words make sense.

Here’s the reassuring part: diapers are sold in Japan, and you don’t need to read much Japanese to pick the right pack. You need your baby’s weight in kilograms and a few words. So we went through the official size charts from the main Japanese makers (Kao, Unicharm, P&G Japan and Daio Paper) and the pages of the stores that sell them, and put the numbers side by side.

How do Japanese diaper sizes work?

Japanese diapers are sized by weight in kilograms. The makers say the weight is a guide, not a rule: your baby’s height, tummy and thighs also change what fits, and so does how much they pee. They ask you to check the range printed on the pack ^{[1] [7]}.

The size names are shared across brands: newborn (新生児, shinseiji), S, M, L, Big (ビッグ, biggu), “Bigger than Big” (ビッグより大きい, biggu yori ōkii) and Super Big (スーパービッグ, sūpā biggu). Some packs add XL or XXL next to the Japanese name ^{[17] [22] [4]}. The kg ranges are close, but they’re not identical, and they can differ between two product lines from the same brand. Pampers, for example, has pull-ups in size M listed as 5–10 kg, 6–12 kg and 5–12 kg, depending on the product ^{[17] [19]}.

Before you shop, write your baby’s current weight in kilograms on your phone. That one number does most of the work.

The tables below show the main lines from each brand (checked on the makers’ pages on November 5, 2026). Lines change often, so treat this as a map, and trust the pack.

Tape diapers (テープ): weight guide by size (maker pages, checked November 5, 2026). Always check the range on the pack.

Size	Merries (Kao)	Moony (Unicharm)	Pampers (P&G)	Goo.N (Daio)
Newborn	Up to 3 kg or up to 5 kg [2]	Up to 3 kg or up to 5 kg [8]	Up to 5 kg [15]	Up to 5 kg [22]
S	4–8 kg [2]	4–8 kg [8]	4–8 kg [15]	4–8 kg [22]
M	6–11 kg [2]	6–11 kg [8]	6–11 kg [15]	6–11 kg [22]
L	No L tape (use pants) [3]	9–14 kg [8]	9–14 kg [15]	9–14 kg [22]
Big	Not listed	Not listed	Not listed	12–20 kg [22]

Note: Merries lines: First Premium tape has two newborn sizes (up to 3,000 g and up to 5,000 g), while Zutto Hada-sara Air-through has one (birth to 5,000 g) ^{[2] [3]}. Pampers’ premium line, Hada-e-no Ichiban (肌へのいちばん), adds a “3S” small newborn size for babies up to 3,000 g ^[16]. MamyPoko makes pants only, so it isn’t in this table ^[12].

Pants diapers (パンツ, pull-ups): weight guide by size (maker pages, checked November 5, 2026). Always check the range on the pack.

Size	Merries (Kao)	Moony Man (Unicharm)	Pampers (P&G)	Goo.N (Daio)
S	4–8 kg [3]	4–8 kg [9]	Not listed	Not listed
M	6–12 kg [3]	Crawling 5–10 kg, standing 6–12 kg [9]	Crawling 5–10 kg, standing 6–12 kg [17]	6–12 kg [24]
L	9–14 kg [3]	9–14 kg [9]	9–14 kg [17]	9–14 kg [24]
Big (XL)	12–22 kg [3]	12–22 kg [9]	12–22 kg [17]	12–22 kg [24]
Bigger than Big (XXL)	15–28 kg [3]	13–28 kg [9]	15–28 kg [17]	13–28 kg [24]

Note: Moony Man also comes in Super Big, 18–35 kg ^[9]. Size M is split into two types at Moony and Pampers: “crawling” (はいはい, hai-hai) and “standing” (たっち, tatchi) ^{[9] [17]}. Merries First Premium pants and Pampers’ premium pants stop at Big ^{[2] [18]}. Moony’s “Tei-shigeki” (低刺激) line is another example with its own size set ^[10].

The fifth big name, MamyPoko (マミーポコ, from Unicharm), makes pants only. Its ranges run a little larger, and the brand itself describes them as “+1 kg larger” (with some sizes excepted) ^[12]:

MamyPoko Pants: weight guide by size (maker page, checked November 5, 2026)

Size	Weight	Source
S	4–9 kg	[12]
M	6–13 kg	[12]
L	9–15 kg	[12]
Big	12–22 kg	[12]
Bigger than Big	13–28 kg	[12]
Super Big	18–35 kg	[12]

We couldn’t find an official comparison between Japanese sizes and sizes at home in the US, UK, Australia or Canada, so we don’t match them up. Go by kilograms.

How do you read a Japanese diaper pack?

You only need a handful of words. These are the ones we saw on the makers’ pages:

Japanese words on diaper packs

Japanese	Reading (guide only)	What it means	Source
テープ	tēpu	Tape style (side tabs)	[8]
パンツ	pantsu	Pants style (pull-ups)	[9]
新生児用	shinseiji-yō	For newborns	[2]
ビッグ / ビッグより大きい	biggu / biggu yori ōkii	Big / Bigger than Big	[24]
スーパービッグ	sūpā biggu	Super Big	[12]
はいはい / たっち	hai-hai / tatchi	Crawling / standing (two kinds of size M)	[17]
適応体重	tekiō taijū	Weight range the diaper is for	[13]
おなかまわり	onaka mawari	Waist (tummy) measurement guide	[25]
〇〇枚	-mai	Number of diapers in the pack	[25]
男女共用	danjo kyōyō	For boys and girls	[13]
男の子用 / 女の子用	otoko no ko-yō / onna no ko-yō	For boys / for girls	[13]
夜用	yoru-yō	For nighttime	[21]
水あそびパンツ	mizu-asobi pantsu	Swim diapers (water-play pants)	[11]

Note: the readings are a rough pronunciation guide we wrote ourselves.

The makers’ pages give every size a kg range, so even with no Japanese at all, the number is what to match against your phone. Some products also come in boys’ and girls’ versions. For example, Oyasuminman night pants come as boys’ and girls’ versions from size L up, while its size M is for both ^[13].

When should you go up a size?

Kao’s Merries page lists signs that it’s time for the next size: the leg or waist feels tight or leaves elastic marks, the tape only reaches the outermost point, the diaper sits well below the navel, leaks are getting more frequent, or your baby’s weight has gone past the range ^[1]. Goo.N gives the navel showing as one of its signs ^[22]. If your baby is near the top of a range, it can be worth buying the smaller pack of the next size up. Merries First Premium, for example, comes in small packs for the newborn (5,000 g) and S tape sizes ^[2].

Tape or pants (pull-ups)?

Tape (テープ) diapers open flat and fasten with tabs at the sides. Pants (パンツ) pull up like underwear. Kao suggests moving to pants once babies are kicking, rolling and crawling, and points out that the sides of pants can be torn open so you can take them off while your baby lies down. It also describes a mix some families use: pants during the day, tape while sleeping ^[5].

The catch is that not every brand makes both styles in every size. From the makers’ current pages:

• Merries: tape goes up to M; L and above are pants only ^{[2] [3]}.
• Moony: tape goes up to L; Moony Man pants go from S to Super Big ^{[8] [9]}.
• Pampers: tape goes up to L; the main pants line starts at M ^{[15] [17]}.
• Goo.N: tape goes up to BIG (12–20 kg); pants start at M ^{[22] [23]}.
• MamyPoko: pants only, from S ^[12].

So if your baby is in size L and uses tape diapers at home, look for Moony, Pampers or Goo.N tape. If your little one is still in S but already rolling off the changing mat, Merries, Moony Man and MamyPoko all make S pants.

Where can you buy diapers in Japan?

These are the places we could confirm on official pages:

• Akachan Honpo (アカチャンホンポ), a baby specialty chain, lists diapers, wipes, formula and baby food among its product categories ^[28]. Its official store search lets you type an address, place name or nearby landmark (the page is in Japanese; a browser translation helps) ^[29]. Its online shop has a diaper section too, which is a handy way to see brands and sizes before you go ^[30].
• Nishimatsuya (西松屋), a baby and kids’ chain, has an official store list by prefecture ^[31], and its official online store has a diapers and toilet category (紙おむつ・トイレ) including its own-brand baby pants ^[32]. It notes that store hours can change at New Year and at other times, so check with the store ^[31].
• Drugstores: the official online store of the drugstore chains Matsumoto Kiyoshi and Cocokara Fine lists diapers, such as Pampers newborn tape and Merries First Premium, in its baby section ^[33], and Kao’s Merries page lists Matsumoto Kiyoshi among its online sellers ^[6]. What each individual store has on the shelf can differ; what each individual store has on the shelf can differ.
• Toys”R”Us / Babies”R”Us is one of the online shops Kao lists for Merries ^[6].

Looking for one brand near your hotel? Unicharm, which makes Moony and MamyPoko, runs an official store finder: choose the product and it shows stores that carry it. It’s in Japanese only, and it warns that stock can run out and stores can move or change names, so check before you go ^[14].

When you get to the store, show this to a staff member:

おむつはどこにありますか?

Omutsu wa doko ni arimasu ka? (“Where are the diapers?”) Then show your baby’s weight in kg on your phone, and they can point you to the right size.

For finding a place to change your baby once you have the diapers, see our guides to nursing rooms in Japan and station toilets and baby seats.

Can you buy diapers tax-free?

Not really, if you’re using them on the trip. Since November 1, 2026, Japan’s tax-free shopping works as a refund: you pay the tax-included price, and the tax comes back after customs confirms your purchases when you leave Japan, within 90 days of buying ^{[34] [35] [39]}. The basic rules from the official pages:

• Only at registered tax-free shops ^[36], and only for 5,000 yen or more (before tax) at the same store on the same day ^{[35] [34]}.
• You can only buy as much as you can take out of Japan yourself ^[37].
• Consumables such as food and cosmetics that you use in Japan don’t get the refund ^{[35] [37] [39]}.
• If even one item from a purchase record isn’t with you at departure, the whole record is refused ^{[34] [35]}.
• How the refund is paid differs by shop, and the shop explains it when you buy ^[38].

The official pages don’t mention diapers by name. But under these rules, diapers you’ll open during the trip aren’t a good fit for a tax-free purchase. If you want to bring a stock of Japanese diapers home, we’d buy those separately from the ones you’ll use, so one opened pack doesn’t put the rest at risk. For how the refund system works step by step, see Pack light, buy in Japan.

Swim diapers, overnight diapers and other types

Swim diapers (水あそびパンツ)

Two of the brands we checked make swim diapers:

Swim diapers: weight guide by size (maker pages, checked November 5, 2026)

Product	M	L	Big	Source
Moony Man Mizu-asobi Pants (水あそびパンツ)	6–12 kg	9–14 kg	12–22 kg	[11]
Goo.N Swimming Pants (スイミングパンツ)	About 6–12 kg	About 9–14 kg	About 12–20 kg	[26]

Read the makers’ warnings before you pack them for the pool:

• Moony says its swim pants can’t fully stop stool or urine escaping in the water and don’t prevent infection, and that some public facilities don’t allow them ^[11].
• Goo.N says its swim pants can’t fully stop watery, loose stool from leaking ^[26].
• Moony’s swim pants don’t contain the absorbent material of a regular diaper, so they can’t be used as a normal diaper ^[11]. Put a regular one back on after swimming.

Rules on swim diapers differ from pool to pool, including hotel pools. Ask the pool before you go. If you’re thinking about onsen (hot spring) baths with a baby in diapers, that’s a separate set of rules; see our onsen and public baths guide.

Overnight diapers (夜用)

Several brands make pants meant for the night. These are what the makers list:

Overnight pants: sizes by product (maker pages, checked November 5, 2026)

Product	Sizes and weights	Source
Merries Gussuri Pants (ぐっすりパンツ)	L 9–15, Big (XL) 12–22, XXL 15–28 kg	[4]
MamyPoko Night Pants (夜用パンツ)	M 6–13, L 9–15, Big 12–22, Bigger than Big 13–28 kg	[12]
Pampers Oyasumi Pants (おやすみパンツ)	M 5–12, L 9–14, Big to Bigger than Big 12–28, Super BIG 18–35 kg	[20]
Pampers Hada-e-no Ichiban night pants	M 5–12, L 9–14, XL 12–22 kg	[21]
Oyasuminman (オヤスミマン, Unicharm)	M 6–12 up to Super Big 18–35 kg; L and up by boys/girls	[13]

Note: Goo.N’s Night Kids Pants (13–25 kg, underwear size 90–120 cm) and Night Junior Pants (15–35 kg, 110–140 cm) are aimed at older children’s bedwetting ^[27].

Bring from home or buy in Japan?

Since diapers are on store shelves in Japan, you don’t need to pack the whole trip’s worth. If we were packing for a week or two with a baby, we’d bring:

• Enough for the flight, the first night and a buffer for a delayed bag or a late arrival.
• A few of your usual diapers for the first days, so there’s no rush to find a store on arrival.
• Bags for used diapers, since you may need to carry them until you find a bin.

Then we’d plan a shopping stop on day one or two, ideally at a store near the hotel, using the store searches above. Japanese packs are sold by count (〇〇枚), and some products come in smaller packs ^{[2] [25]}, which can be easier to carry around than a big bundle. If you expect to shop on your trip, buying diapers where you’re staying is one way to free up suitcase space for the way home.

If your baby is sensitive to a change of diaper, or wears an unusual size, packing more of your usual brand is the calmer choice.

For the rest of what to pack and what to buy in Japan, see our Japan with a baby packing list.

A quick checklist

Before you go

• Write your baby’s weight in kilograms on your phone.
• Decide tape or pants, and check which brands make that style in your size (tables above).
• Pack diapers for the flight, the first night and a buffer, plus bags for used diapers.
• Save the Akachan Honpo or Nishimatsuya store search, or Unicharm’s store finder, for the area near your hotel.

At the store

• Look for テープ (tape) or パンツ (pants), then the kg range on the pack.
• At size M, check whether it says はいはい (crawling) or たっち (standing).
• Show おむつはどこにありますか? to a staff member if you can’t find the aisle.

Swim and night

• Ask the pool whether swim diapers are allowed, and remember they can’t fully stop leaks.
• Put a regular diaper back on after swimming.

Tax-free

• Consumables used in Japan don’t get a refund, so diapers for the trip aren’t a good fit. If you buy items to take home tax-free, keep them on a separate receipt, and remember the minimum is 5,000 yen before tax at one store on one day.

Questions parents ask

Are Japanese diaper sizes the same as in the US, UK or Australia?

We couldn't find an official comparison, so we don't match them up. Japanese packs show a weight range in kilograms. Choose by your baby's weight in kg and read the range on the pack, because it differs a little by brand and product line.

What's the difference between tape and pants diapers in Japan?

Tape (テープ) diapers open flat and fasten with side tabs. Pants (パンツ) pull up like underwear. Kao, the maker of Merries, suggests pants once babies start kicking, rolling and crawling, and notes the sides of pants can be torn open to take them off while your baby lies down. Not every brand makes both styles in every size.

Can I buy diapers tax-free in Japan?

Since November 1, 2026, tax-free shopping works as a refund after a customs check when you leave. Consumables such as food and cosmetics that you use in Japan don't get the refund, and if one item from a purchase is missing at departure, the whole purchase is refused. The official pages don't name diapers, but diapers you plan to use during the trip aren't a good fit for tax-free buying.

Can I use Japanese swim diapers in a hotel or public pool?

It depends on the pool. Moony says its swim pants can't be used at some public facilities, Moony says its swim pants can't fully stop leaks in the water, and Goo.N says its swim pants can't fully stop watery, loose stool from leaking. Ask the pool before you go.