The rating system has been created by the CCG. Ghouls are rated based upon various factors, including their basic strengths, activity levels, influence and hostility towards investigators.
In addition to the ghoul's individual ability, the actual damage caused by the ghoul is also evaluated. The rating is set in consideration of the predation and killing incidents committed by the ghoul.

For some ghouls, their influence over other ghouls is also taken into account when ratings are given.
The rating extend from SSSSS (the most powerful ghoul) to C (the weakest ones). The once who have a '~' in their rank are considered as the ghouls of at least this rank. So in theory they can be even more dangerous and so they can have a greater rating.

Characteristics:

• More than the entire CCG can handle.

Corresponding ghoul:

• Kaneki Ken

Kaneki Ken:
Originally born as a human, his encounter with a female ghoul under the name of Kamishiro Rize forced him to undergo emergency surgery procedures after his assault by her. Cunning and manipulative, Rize uses her charms and Kaneki's attraction toward her as a means of getting her next "meal." After the attack, Kaneki is rushed to the hospital in a half-dead state with Rize. A doctor of the name Kanou, who secretly experiments with ghouls, humans, and half-ghouls, transplants what Kaneki believes to be a kidney into his body as a means of saving his life in the dire situation. Soon he learns that he had part of Rize's kagune transplanted into him, becoming the first of many human-ghoul experiments Kanou will conduct.

Characteristics:

• More than several of Special Class Investigators are needed.

*No ghouls with this rating present

Characteristics:

• Several of Special Class Investigators are needed.

Corresponding ghoul:

• Shachi

Shachi:
Matasaka Kamishiro (神代 叉栄, Kamishiro Matasaka) is the former leader of the ghouls in the 6th ward. He inherited the surname "Kamishiro" from his mentor. He looked after Rize Kamishiro, who was on the run from V at the time, as his foster daughter. Most people refer to him by his nickname Orca or Shachi (鯱, Shachi).

Characteristics:

• More than 3 of Special Class Investigators are needed.

Corresponding ghouls:

• Eto
  　
• Yoshimura

"Acts of taking are equally evil. We, from the moment of birth, continue to take: food, people that got involved with us, even our own flesh and blood. For as long as we live, we continue to slaughter, kill, take. Life is to constantly sin. Life is evil itself. I am aware of it, I am evil... and so are you all."
— Yoshimura

Characteristics:

• Couple of Special Class Investigators are needed.

Corresponding ghouls:

• Yakumo Oomori
  　
• Kuki Urie
  　
• Roma Hoito
  　
• Seidou Takizawa

Yakumo Oomori:
Yamori developed an arrogant and sadistic personality that mirrored his interrogator as a means of escaping the reality of his torture. He was a manipulative and deceitful ghoul who would be violent in order to get what he desires.

　
• Noro
  　
• Tatara
  　
• Hinami Fueguchi
  　
• Rize Kamishiro
  　
• Touka Kirishima

"Tomorrow is another day on this rocky path we walk, never knowing stability. But I believe. I believe that the sun shines after a downpour."
— Hinami Fueguchi

　
• Big Madam
  　
• Rio
  　
• Ayato Kirishima

Ayato Kirishima
Ayato was an arrogant, brash teenager, with a similar hot-blooded attitude resembling his sister's, while he normally displayed either a scowl or menacing smirk on his face. Other than his physicalities, he shared many similarities with Touka, such as his tendency to use language that is often uncouth or inappropriate.

　
• Kaya Irimi
  　
• Enji Koma
  　
• Donato Porpora
  　
• Kurona Yasuhisa

"How cruel it is. Cruel to be one of those who can only but watch over others."
— Donato Porpora

Characteristics:

• Equivalent to the ability of an average Special Class Investigator or an average Associate Special Class Investigator.

Corresponding ghouls:

• Demon Yamada
  　
• Miza Kusakari
  　
• Naki
  　
• Nutcracker
  　
• Shuu Tsukiyama

"Live beautifully with your head up high, just like that rose on your chest."
— Shuu Tsukiyama

Characteristics:

• Comparable to a First Class Investigator. These ghouls are usually set as a target and some ghouls might develop a second tail/tentacle.

Corresponding ghouls:

• Yumitsu Tomoe
  　
• Hooguro
  　
• Shousei Idera
  　
• Bin brothers

Bin brothers
Among Aogiri's members, they had a relatively moderate personality. During a fight, while one was about to be defeated, they used mockery as a means to trick their opponent. They had sworn their allegiance to the One-Eyed King and idolized Aogiri's ideology.

　
• Nishiki Nishio
  　
• Karao Saeki
  　
• Skull Masks Leader

"The normal days which seemed natural will crumble in an instant. The end... always comes in the blink of an eye."
— Nishiki Nishio

Characteristics:

• Comparable to a Rank 1 to Rank 3 Investigator. These ghouls should have their Kagune mastered and are usually a small threat to the CCG.

Corresponding ghouls:

• Akashi Kobayashi
  　
• Average Aogiri Tree member

Akashi Kobayashi
As a way to blend in with the human society, Kobayashi often portrays himself to be quite a cheerful, friendly man. While his occupation is associated with transport, his main hobby is making confections; something he finds comfortable, but is flustered about admitting. As a ghoul, Kobayashi seems proud of the extraordinary sense of smell his nose possesses.

Characteristics:

• Ghouls of smaller ability, these ghouls usually can't fight any ghoul investigators and only attack unarmed humans.

*The rest of ghouls