ForgottenLife
well he should be around 15-16 I suppose he is 13 when Donzo read his profile and when he 'killed' Donzo. After which he train he sage art for more than 6 months and train the nature transformation for months too. The Uchiha incident afterward the Old hag say that 'I don't need a 14-15 brat to teach the elders and stuff' so now he is probably 15-16 years I guess