Judge Yoda by his size, do you? Well, Dr. Rhett Allain does. He's a professor of physics at Southeastern Louisiana University. In the past, he's calculated Darth Vader's weight and how long it would take for an AT-AT to hit the ground. He wanted to know how much Yoda weighs. And since the Jedi Master is shy about the issue, Allain had to calculate the results from The Empire Strikes Back.
Allain assumes that Dagobah has the same gravity as Earth, that Luke Skywalker is 5'9" and weighs 150 pounds, and that The Force is not in play against gravity while Luke is carrying Yoda. You can read all of his equations and rationale here. Yoda, Allain argues, weights 43.7 kilograms.
-via Lost at E Minor