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 post-season tournament — which follows a standard, sporting tournament bracket.