At the Kodokan we consider the individual's unique circumstances and abilities. BJJ is a martial art that can be practiced by people of all ages, and there is no specific age that is considered to be the "right" age to start.
That being said, it is generally recommended that children be at least 5 years old before starting BJJ, as younger children may not have the necessary attention span or physical coordination to fully participate in the class. For older children and teenagers, BJJ can be a great way to improve physical fitness, self-discipline, and confidence.
For adults, there is no upper age limit for starting BJJ. Many people discover the martial art later in life and find that it is a rewarding and challenging activity that can improve physical fitness, mental focus, and stress relief.
Ultimately, the most important factor in deciding when to start BJJ is whether or not the individual is interested in the martial art and willing to commit to consistent training. As with any physical activity, it is important to listen to your own body to determine if BJJ is a suitable activity for you.
In conclusion, there is no specific age that is considered the "right" age to start practicing Brazilian Jiu Jitsu. Children should be at least 5 years old, and adults of any age can benefit from the physical and mental challenges of the martial art. The most important factor is the individual's interest and willingness to commit to consistent training.