What is a novella if I don’t know the word count?

Normally the criteria for a novella is determined by word count, which is fine. But it isn’t very helpful for someone trying to pull together nominees for a novella category because that information isn’t readily available. So a new criteria is needed based on info that IS readily available. Two that I have easy access to are page count (actual or estimated) and file size. And if that is what I have to work with then I have to come up with my own parameters that I’m comfortable with.