The standards for grading and belt promotions vary between schools, but the widely accepted measures of a person's skill and rank in Brazilian Jiu-Jitsu are:
The amount of technical knowledge they can demonstrate, and
Their performance in sparring and competition.
Technical knowledge is judged by the number of techniques a person can perform, and the level of skill with which he performs them in sparring and competition. This allows for smaller and older practitioners to be recognized for their knowledge though they may not be the strongest fighters in the school. It is a distinctly individual sport, and practitioners are encouraged to adapt the techniques to make them work for their body type, strategic preferences, and level of athleticism. The ultimate criterion is the ability to execute the techniques successfully, rather than strict stylistic compliance.
Competitions play an important role in Brazilian Jiu-Jitsu gradings, as they allow an instructor to compare the level of his students against those of the same rank from other schools. A belt promotion may be given after success in a competition, particularly at the lower belt levels. A promotion might also be awarded when a person can submit most people in his school of the same rank, e.g. a white belt who consistently submits most other white belts in sparring and is starting to catch blue belts.
The high level of competition between schools - and its importance for belt promotion - is also considered to be one of the key factors preventing instructors from lowering standards or allowing people to buy their way up the belts. Instructors may also take the personality of the person and their behavior outside of class into account, and may refuse to promote someone if they exhibit antisocial or destructive tendencies. It is by these and other criteria that most instructors promote their students. Some schools may also have formal testing which might include oral or written exams.
Some schools use a stripe system for each belt level, indicating progress through that belt.
Adult belt colors (16 and over) White
Junior belt colors (15 and under) White
Some schools use slightly different belt systems, such as having more colored belts before blue belt, but the above are the only widely accepted ranks as they are the standards for tournaments. There are minimum age requirements for belt promotions. Blue belts are never awarded to anyone under the age of 16. For promotion to black belt the minimum age is 19 years old according to the main regulating body of Brazilian Jiu-Jitsu, the International Brazilian Jiu-Jitsu Federation.
Stripes may be awarded to any rank below black belt, but like the belts themselves, they tend to be given at the instructor's discretion, and may be in recognition of accomplishments like noticeable improvement or tournament victories. However, not all schools award stripes, or award them consistently, so the number of stripes a person has is not necessarily a good measure of their accomplishments or time in training. When they are used, it is standard for a student to receive four stripes before being promoted to the next rank.
Black belts can receive degrees, up to 9th degree, for as long as they train or teach the art. At 7th degree, the black belt is replaced by an alternately red and black belt. At 9th & 10th degree, the belt becomes solid red. Only the founding Gracie Brothers Helio, Carlos & his brothers will ever have the 10th degree red belt. The Gracie family members who are 9th degrees belt holders are Carlson Gracie, Reylson Gracie, Relson Gracie, and Rorion Gracie.
BJJ differs in some aspects from other martial arts in the criteria for grade promotion, which is almost exclusively based on practical expertise in randori (free sparring, or rolling) and championship results. It's expected, although not always the case, that any BJJ black belt is extremely proficient in every applied aspect of BJJ and also perform well in competition. Less emphasis is given to theoretical and background knowledge. Rarely is any formal test undertaken for the grading, which is based mainly in observation at every-day practice sessions. By contrast, in Judo, practical knowledge and expertise in shiai (competition) and/or randori alone would not normally give an athlete the black-belt grade, as knowledge of technique names and Kata demonstration are necessary (the exception is promotion by Batsugun.)
There is a vast difference in how often belt progression takes place, and the requirements for the progression..More traditional schools and especially Gracie-affiliated schools believe that black belt cannot be achieved in under 8 to 10 years, while some schools allow students to achieve black belt more quickly.