I have a friend who works in private equity and he usually targets 100 million for investment then flip in 5 years 

I think that's actually a good rule for medium sized. I'm a little biased toward the tiny side of things so I was thinking more so small to medium rather than what is medium on an absolute scale.

k00b

Bell_curve

Series A or later probably, but it's hard to define exactly what medium means here. Ideally some traction/revenue to stand on. It's less employee count because there are mega-staffed super-early companies these days. Maybe it's a maturity level thing? 

I once gave a talk at Cal along these lines. Back then I said it meant "profitable or nearly so" but times have changed some.

Stacker Saloon

saloon

How do you define medium-sized? Certain company age? Certain employee count? Obviously it's all relative, but I'd be curious to hear your opinion on it.