A long time! I spent three years at University doing my first degree, and then four years doing my PhD. So that’s seven years of formal training. But when you’re a scientist you never stop learning new skills, so the six years I’ve spent working as a scientist since my PhD have also been part of my training.
To be honest, I have never felt as if I had finished the training, because there is always so much to learn. Anyway, technically, it was a 5 years degree, a 3 years PhD (that is for the formal training) and 4 years and half postdoc to be where I am now. The postdoc position is a tricky one, because even if in theory you are a fully trained scientist, some people can still consider you in training (…and use it as an excuse to pay you less 🙁 )