Measuring a bottom bracket

[blokefromstoke]

Did a quick search so hopefully this isn't a repeat thread. Can anyone tell me how to properly measure a bottom bracket? I have my dads old Raleigh 3speed sit up and beg bike. I was looking at converting it to an ebike as its bullet proof and comfy so should make a good commuter. When measuring the bottom bracket its 71mm without the cup(think that's what its called, bit on the left haha), 75mm with it, and when looking at a bafang mid drive it says no more than 73mm. So i wasn't sure if the bottom bracket was just the tube or the whole thing??

 

[D8ve]

It's the empty tube bit with nothing attached. The BBS replaces everything.
If it was a mm or two out you could even file off a little. I had to remove a bit from inside the bracket as there was a lip fowling the BBS when I did mine. Just visible with the white grease

 

[blokefromstoke]

Cheers for clearing that up, like I said wasn't 100% sure either way