Measuring turbo size

[2001cumminsman]

where to do you measure the turbo compressor wheel? on the smaller part towards the air filter or the big part towards the housing, its a massive turbo off of a john deere tractor, its a schwitzer turbo and from what ive found on it its a 64mm but idk

 

[FosterW]

Most measurements you see are the inducer size. Towards the inlet of the compressor housing.

 

[FosterW]