The percentage of ‘s’ character in ${\text{sp}}^2$  hybridisation is

$33.33\%$ . In ${\text{sp}}^2$  hybridisation 1 s orbital and 2 p orbitals combined together to form three ${\text{sp}}^2$  hybrid orbitals. In these ${\text{sp}}^2$  hybrid orbitals the s character is $33.33\%$  and p character is $66.66\%$ .