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Show classes and size categories

By the koi.wiki editorial team · Updated

Key facts: Koi shows divide entries into size categories measured in bu (cm bands) and variety classes grouped by pattern type, with separate male classes in some systems.[1][2]
At nishikigoi shows, each koi is “benched” into a size division called bu (歩), based on body length from nose to tail, and a variety class based on its pattern and coloration. According to Zen Nippon Airinkai (ZNA), size has no relation to weight or body thickness and is purely a length measurement[1]. Variety classification determines which koi varieties compete against each other, while size classification groups koi of similar length so young, small fish are not judged against mature giants.

Bu size divisions

According to ZNA, bu divisions at the All Japan Nishikigoi Show run in 5 cm steps from 15 Bu (15 cm and under) up to 90 Bu (over 85 cm up to 90 cm), with an additional "Over 90 Bu" division for koi longer than 90 cm[1].
ZNA bu size divisions
DivisionLength
15 Bu15 cm and under[1]
20 Buover 15 cm up to 20 cm[1]
30 Buover 25 cm up to 30 cm[1]
45 Buover 40 cm up to 45 cm[1]
55 Buover 50 cm up to 55 cm[1]
70 Buover 65 cm up to 70 cm[1]
90 Buover 85 cm up to 90 cm[1]
Over 90 Buover 90 cm[1]
A separate commercial source, the US dealer Kodama Koi Farm, describes a coarser "general" set of show size categories in roughly 10 cm steps, from 15 Bu (under 15 cm or 6 in) up to 75 Bu and 75 Bu+ (30 in and above), with approximate inch equivalents given for US audiences[6]. This differs from the finer 5 cm ZNA scale, illustrating that bu bands are not universally standardized across all shows[1][6].Some local shows define sizes by numbered classes rather than bu labels. The ZNA SoCal Koi Show, for example, uses nine numbered size classes from Size 1 (under 20 cm) to Size 9 (90 cm and above), each tied to a points value used to limit how many fish an exhibitor can enter per tank under a "fish load formula"[7].

Variety classes

ZNA divides nishikigoi into 17 varieties for show and appreciation purposes, even though it notes there are over a hundred named varieties overall; these 17 are split into Group 1 (varieties 1–5) and Group 2 (varieties 6–17) for the purposes of ZNA's Zipangu Prize[3]. The 59th ZNA International Koi Show entry rules list these numbered codes explicitly: 1 Kohaku, 2 Taisho Sanshoku, 3 Showa Sanshoku, 4 Utsurimono, 5 Kinginrin 1, 6 Bekko, 7 Asagi, 8 Shusui, 9 Koromo, 10 Kawarimono, 11 Goshiki, 12 Hikarimono, 13 Hikari Utsurimono, 14 Kinginrin 2, 15 Mujimono, 16 Hikari Mujimono, and 17 Tancho[2].A separate ZNA America classification document used for the 2026 ZNA America Koi Show lists the same 17 numbered variety groups with specific sub-varieties, such as Hi Utsuri, Ki Utsuri, and Shiro Utsuri under Utsurimono, and Ai Goromo, Sumi Goromo, and Budo Goromo under Koromo, plus an 18th "Male" classification covering all varieties[8].The American Koi Judges Association (AKJA) publishes a simpler list of recognized classifications, including Kohaku, Sanke, Showa, Utsurimono, GinRin, Doitsu, Tancho, Asagi/Shusui, Koromo/Goshiki, Bekko, Hikari Moyomono, Hikari Mujimono, Hikari Utsuri, Mujimono, Kawarigoi, and Longfin, while noting that show organizers may adapt the structure to local practice[4].The dealer Kodama Koi Farm describes a further set of "variety categories" used at its own Kodama Koi Show, including Hirenaga as a distinct category alongside the more typical groupings; this is a commercial source describing a specific event rather than a universal standard[6].Local club rules can diverge further: the ZNA SoCal registration packet groups varieties into "Group A" (Kohaku, Sanke, Showa, Utsurimono) and a broader "Group B" covering Bekko, Tancho, Asagi/Shusui, Koromo/Goshiki, Kawarimono, Gin Rin B, Hikari Moyomono, Hikari Utsurimono, Hikari Mujimono, and Mujimono[7].

Male classes

At the ZNA International Koi Show, six extra categories are added specifically for male koi measuring 55 Bu and larger: Male Kohaku, Male Taisho Sanshoku, Male Showa Sanshoku, Male Utsurimono, Male Kinginrin 1, and a combined "Male 2" class, assigned to Group 1 or Group 2 for Zipangu Prize purposes[2]. ZNA's variety overview confirms that six extra categories for male koi over 50 cm are added specifically for show judging, separate from the 17 standard varieties[3].The dealer Kodama Koi Farm states, through its representative Taro Kodama, that male koi tend to perform better in smaller size categories (up to about 20 inches) due to stronger coloration, while female koi are generally favored in larger size categories for major titles such as Grand Champion, Reserve Grand Champion, or Mature Champion; this reflects one dealer's stated experience rather than an official show rule[9].

Championship tiers by size group

Under the ZNA 59th International Koi Show rules, size bands are grouped into named championship tiers judged across different tank areas. Smaller sizes (15–35 Bu) fall under a "Baby Champion" and "Young Champion" range in the Plastic Bags Area; mid sizes (40–65 Bu) correspond to "Adult Champion" and "Mature Champion" in the Tank A Area; and the largest sizes (70–90 Bu and Over 90 Bu) correspond to "Superior Champion" and ultimately "Majestic Champion" in the Tank B Area[2].Similarly, the 12th All Asia Cup Koi Show in the Netherlands selected a Grand Champion from the three best koi measuring 80 cm and above (supplemented from 75 cm if needed), with tiers such as Superior Champion, Mature Champion, Adult Champion, Young Champion, and Baby Champion awarded separately within Gosanke (A), non-Gosanke (B), and a further non-Gosanke group (C), each by size[10]. Jumbo koi awards in that event were drawn specifically from koi 85 cm and larger, with judging emphasis on size and body conformation over pattern quality[10].

Junior shows and regional variants

Some shows use entirely separate size ranges for young or small koi. The All Japan Young Koi Show, organized by the All Japan Nishikigoi Promotion Association (JNPA), allows entries from 12 cm up to 63 cm[5]. The International Junior Koi Show, first held in 2013 and organized through Niigata, was created specifically for koi under 36 cm in response to the growth of fish-tank keeping and demand for smaller koi[5].International shows outside Japan also adopt their own size and variety counts. The inaugural 1st Asia Cup Koi Show in Singapore in 2008 categorized entries into 14 sizes and 16 varieties, judged by a panel including senior judges from ZNA and from the All Japan Nishikigoi Promotion Association (referred to there as Shinkoukai)[11].A Brazilian koi show report notes that entries were distributed across size categories known as "BU's" in a relatively balanced way, with Gosanke varieties such as Kohaku and Showa Sanshoku drawing the largest number of entries, according to a secondary source[12].

Common questions

What does "bu" mean at a koi show?
Bu is the unit used to classify koi by size at a show, based on body length from nose to tail rather than weight or thickness, with divisions such as 15 Bu, 55 Bu or 90 Bu marking length bands[1].
How many bu size divisions does ZNA use?
ZNA's All Japan Nishikigoi Show uses divisions in 5 cm steps from 15 Bu (15 cm and under) through 90 Bu (up to 90 cm), plus an "Over 90 Bu" division for koi longer than 90 cm[1].
Are there separate classes for male koi?
Yes, the ZNA International Koi Show adds six extra classes specifically for male koi 55 Bu and larger, covering Male Kohaku, Male Taisho Sanshoku, Male Showa Sanshoku, Male Utsurimono, Male Kinginrin 1, and a combined Male 2 class[2].
Do all koi shows use the same size categories?
No. ZNA uses 5 cm bu bands[1], a dealer-published general scale uses roughly 10 cm bands with inch equivalents[6], and ZNA SoCal uses nine numbered size classes tied to a points-based entry limit system[7].
Why do some shows have separate junior or small-koi categories?
Events such as the All Japan Young Koi Show (entries 12–63 cm) and the International Junior Koi Show (koi under 36 cm) were created to accommodate smaller koi and growing interest in fish-tank-scale keeping[5].

References

  1. ^ Keep Nishikigoi | Zen Nippon Airinkai. Zen Nippon Airinkai. zna.jp/en/keep-nishikigoi/keep-nishikigoi/. Retrieved November 2026.
  2. ^ 59th ZNA International Koi Show entry rules (ZNA). Zen Nippon Airinkai. zna.jp/wp-content/uploads/2023/07/59th-zna-koishow.pdf. Retrieved November 2026.
  3. ^ Varieties of Nishikigoi | Zen Nippon Airinkai. Zen Nippon Airinkai. zna.jp/en/keep-nishikigoi/varieties-of-nishikigoi/. Retrieved November 2026.
  4. ^ AKJA Classifications – American Koi Judges Association (AKJA). American Koi Judges Association. akjajudges.com/akja_classifications/. Retrieved November 2026.
  5. ^ History of Nishikigoi show - All Japan Nishikigoi Promotion Association. All Japan Nishikigoi Promotion Association. jnpa.info/en/show/history/. Retrieved November 2026.
  6. ^ Preparing for Koi Competition and Tips for Winning Koi Shows. Kodama Koi Farm (koi dealer). kodamakoifarm.com/koi-show-competition-tips-preparation/. Retrieved November 2026.
  7. ^ ZNA SoCal 50th Annual Koi Show exhibitor registration packet (2026). znasocal.org. znasocal.org/wp-content/uploads/2026/02/2026-entrant-registration-1…. Retrieved November 2026.
  8. ^ Koi classification (ZNA 2021), NMZNA 2026 show documents. nmzna.net. nmzna.net/2026%20Show%20Docs/NMZNA%202026%20Koi%20Classification%20…. Retrieved November 2026.
  9. ^ Male vs Female Koi Fish: How to Identify Gender and Koi Sexing Tips. Kodama Koi Farm (koi dealer). kodamakoifarm.com/male-koi-vs-female-koi-fish/. Retrieved November 2026.
  10. ^ Jureren tijdens de 12e ALL ASIA CUP KOI SHOW - Besems.eu. besems.eu. besems.eu/2019/05/09/jureren-tijdens-12e-all-asia-cup-koi-show/. Retrieved November 2026.
  11. ^ 1st Asia Cup Koi Show press release, 29 April 2008. yumpu.com. yumpu.com/en/document/view/47645378/1st-asia-cup-koi-show-inaugural…. Retrieved November 2026.
  12. ^ Beleza e tradição em destaque na 43ª Exposição Brasileira de Nishikigois. Fish TV. fishtv.com/noticias/geral/beleza-e-tradicao-em-destaque-na-43-expos…. Retrieved November 2026.