All this information comes from the blueprints for the characters that were found in Sister Location. You can check that on each characters image gallery here in the wiki.
Considering this, I think you could safely assume each animatronic has an average height of 6 feet. But, if we were to consider how every other animatronic wears a costume, differently to the Funtime robots, and that the average height for an american man is 5 feet and 9 inches, I think somewhere close to 7 feet wouldn't be off, especially regarding spring lock suits.
i think the fnaf 1 animatronics would be bigger than the funtime ones, the SL characters seem to have more modern technology, like face plates and more detailed endoskeletons, so it would make sense to make them more human sized
Nah, SL animatronics are the biggest as they're designed to capture kids though if we wanted to go bigger we could bring up the Twisted animatronics which can swallow up a person bigger than a small child.
The Toy animatronics seem rather jokingly small and I swear I almost choked on my spit when I read Baby was apparently 7 feet tall for the first time. One of us is crazy Scott and for once I'm not sure it's me.