Extraction efficiency calculation

[beerisyummy]

I've been BIAB and using a dunk sparge. To calculate extraction efficiency, I want to take a gravity reading from the BIAB equivalent of "all runnings" - that is all the water that makes it into the boil, mash + dunk. Am I right?

 

[IslandLizard]

That's correct, as long as you mean:
all the water wort that makes it into the boil [...]

Being the sum of all runnings ending up in the kettle.