what is the average age for toilet training the physical maturity and readiness skills needed for successful toilet learning appear at the same time in girls and boys between 18 and 30 months of age the average age for girls to be toilet trained is 29 months and for boys it s 31 monthskeep in mind that these are averages ninety eight percent of kids are trained by 36 months of agehe physical maturity and readiness skills needed for successful toilet learning appear at the same time in girls and boys between 18 and 30 months of age the average age for girls to be toilet trained is 29 months and for boys it s 31 months