u/BaddestMofoLowDown

I am sourcing strongman equipment from China but I know zero about steel pipes and their load-bearing requirements. I know the length of the pipes and their varying outer diameters but I am unsure of the wall thickness needed. 2mm? 3mm? 4mm? So, I am hoping there is a calculator or formula I can use.

For context, I am trying to get custom axles and dumbbell handles made but I don't want the pipe to crumple in the middle because the wall is too thin. This is an example of a strongman axle where weight is loaded on either side.