GMCA organizes the Mental Calculation League and hosts weekly, remote competitions between elite mental calculators from around the world. Interested calculators can find a registration form here and detailed league instructions here. League competition adheres to the following outline:

-Each competitor engages in one 10-20 minute match-up per week. The two competitors engage in a direct head-to-head match-up consisting of a variety of task formats randomly generated. This website has a league simulator that reflects the type of question formats used in competition.

-At the conclusion of the season, the top half of competitors qualify for the playoffs stage. At the end of the playoffs stage, the top half of competitors qualify for the finals.