Spotted turtle sexing

[Herpin man]

At what age or size can the gender of spotted turtles typically be determined?

 

[Markw84]

Because husbandry can dramatically change growth rates, I find size is much more the consideration than age. Normally by 3-1/2" the dark face of the male starts to become obvious, and the tail will be getting visibly larger. I think in most cases that should be their 3rd year given good husbandry.