Game Speed is a rough measure of how much time each player has to complete a game based on the time control. It allows for easier comparison between different types of time controls, and for simple categorization of games for rating purposes.
Which game would require you to move faster on average, a game at G/3+2 or a game at G/5+0? Which would allow more total thinking time, a game at G/15+10 or a game at 30/15+0? Game Speed simplifies the comparisons by creating an objective measurement formula for converting a time control into the total time it typically allows each player.
Game Speed is measured in minutes and is defined as the maximum time available to complete 40 moves, taking into account both the base time and increment. 40 moves is representative of the length of a typical game. Of course many games will last longer, but usually as part of a technical endgame phase rather than a strategic middlegame phase. All things considered, 40 moves works pretty well as a measure of the "decision point" of an average game.
These are the speed measures and calculations for each of the standardized time controls used on Caissa.com:
|Time Control||Game Speed||Calculation|
|G/2+1||2.6 mins||2mins + 1sec x 40|
|G/3+2||4.3 mins||3mins + 2sec x 40|
|G/5+0||5 mins||5mins + 0sec x 40|
|G/6+3||8 mins||6mins + 3sec x 40|
|G/10+0||10 mins||10mins + 0sec x 40|
|30/15+0||20 mins||15mins x 40/30 + 0sec x 40|
|G/15+10||21.6 mins||15mins + 10sec x 40|
|G/30+0||30 mins||30mins + 0sec x 40|
|G/25+10||31.6 mins||25mins + 10sec x 40|
|30/30+0||40 mins||30mins x 40/30 + 0sec x 40|
|30/60+0||80 mins||60mins x 40/30 + 0sec x 40|
|G/90+30||110 mins||90mins + 30sec x 40|
As you can see, a G/3+2 game is slightly faster than a G/5+0 game, and a G/15+10 game is just a bit slower than a 30/15+0 game.
Finally, game speed serves as the basis for dividing live games into rating categories. A game speed of less than 10 mins is considered Blitz, from 10 mins to 30 mins is considered Fast, and anything above 30 mins is considered Slow.