Kendo uses the traditional Japanese grading system which consists of Kyu (級) and Dan (段) grades, very similar to other martial arts (like Judo and Karate). In those systems, Kyu grades are the coloured belts, and Dan grades are the black belts. However, please note that 1st Dan in Kendo, despite being a "black belt" in other systems, is still very much considered a beginner's grade. A closer equivalent to the level of mastery typically associated with black belts in other systems would be a Kendo 3rd Dan - this is the point at which a kendo practitioner is expected to have mastered the mechanics of the fundamentals of kendo.
The Kyu grades start at 6th Kyu, and progress downwards to 1st Kyu. You will often hear this grade referred to as ikkyu (from the Japanese work for 1st Kyu). Then, the grades go to ascending order, starting from 1st Dan (or shodan) up to the coveted 8th Dan. While some 9th Dan masters are still alive, the grade is no longer awarded. The grades get progressively and exponentially more challenging, with some saying that the gap between 7th Dan and 8th Dan is the same as the gap between 1st Kyu and 7th Dan.
Grading is an integral part of kendo - it is a way of reflecting on your progress and achievement, and staying focused on what is ahead.
6th - 2nd Kyu are governed and administered by the dojo/club that you train with. It is at their discretion whether or not to award grades to its members. At the moment, Doshinkenyukai York does not hold internal gradings so the first grade our members get is 1st Kyu.
1st Kyu onwards, you must attend a national grading regularly hosted by the British Kendo Association around the country where you will be examined by a panel of impartial judges. A national grading typically consists of kirikaeshi (basic cutting exercise), tachi-ai (sparring) , and kata (pre-set forms done in a pair, using wooden swords). You must successfully demonstrate the criteria the judges are looking for in each category in order to pass the grading.
You can find the grading syllabus for each assessed grade on the BKA website.
Kendo does not use belts to denote grade and there are no other visible markers indicating a practitioner's grade; this is in part to teach humility and to only judge a fellow kendoka not by a colour of their belt but by their actual ability.
A brand new beginner starts with no grade, and through hard work and consistent practice they can expect to reach 1st Kyu after approximately two years of practice (assuming one, two-hour practice a week). Keeping the same levels of hard work, they can expect to reach 1st Dan after another year.
However, bear in mind that these are very rough guidelines, and are nothing more than an approximation. Some people progress very quickly, while others are a lot slower, and both are okay.