I found this off of Tumblr, it helped me a little determining the height of all the bots and humans too.

Optimus Prime: 9 meters (10.5 meters after upgrade)
Bulkhead: 7 meters
Ratchet: 7 meters
Bumblebee: 5.8 meters
Arcee: 4.8 meters
Cliffjumper: 5.6 meters
Jack Darby: 1.77 meters
Miko Nakadai: 1.45 meters
Rafael Jorge Gonzalez Esquivel: 1.21 meters
June Darby: 1.75 meters
Agent William Fowler: 2.10 meters
Wheeljack: 6 meters
Smokescreen: 6.6 meters
Ultra Magnus: 8.8 meters
Megatron: 11 meters
Starscream: 7.1 meters
Soundwave: 7.4 meters
Breakdown: 7.4 meters
KnockOut: 6.3 meters
Airachnid: 5.1 meters
Vehicons: 6.5 meters
Dreadwing: 9 meters
Insecticons: 10.2 meters
Skyquake: 9 meters
Silas/ Colonel Lelan Bishop: 2.2 meters
Shockwave: 7.8 meters
Predaking: 11 meters