i knew it up to 10x10 by age ~6. then moved to the UK and had to learn till 12. then till 15x table - i never really learnt it super well past 11/12 (the ones i learnt at a younger age) even today i could answer any till 12x12 in a flash but not beyond.. (eg 13x14 would take me disprportionately longer than up till 12x12)