Average IQ of chess grandmaster
1742 chess GMs
605M chess players (chess gms are on average 4.72 SD above mean)
correlation between chess and iq in unranked samples is 0.32 (probably closer to 0.4 when you account for measurement error in both constructs)
Easy estimate: 4.72 x 0.4 = 128. Difficult to tell given the g-loading of chess seems unreasonably low in research studies