How much is "a ladleful"? I have a recipe that asks for "a ladleful" of something. The recipe book usually uses imperial weights and volumes, that I can convert to my metric units that I hold so dear.

As I understand it, a ladleful is the volume necessary to fill a ladle - but how much is it? A ladle can take on various sizes, so I guess it wouldn't make much sense to not normalize it in any way (like, a cup is eight ounces).

EDIT:
As suggested in the comments, I want to mention it is "a ladleful of sourdough starter" that I should add to 2 pounds 7 ounces / 1.1 kg of rye flour and 2.5 cups of water. I'd normally go with about 500g of starter, but that seems like a big ladle to me.
Every sourdough starter has different characteristics, a ladleful of one will give a different result from the same amount of another. The recipe is right in that there's no way to say what result you are going to get, so why be exact. 

The point I would make is that you want repeatibility, and the capability to adjust your amounts over time to suit your taste. So whatever you use to get it out (ladle, spoon, measuring cup, hand) I would weigh and record how much starter you use, you can add more or less and see how you get. As long as you keep using the same starter you can adjust to your taste.