## How do things like oats affect hydration?

I have a recipe for a basic sandwich loaf that uses rolled oats that I'm trying to play around with, but to do some calculations I want to figure out what my starting hydration is. If the recipe has about 3cups of flour and 1 cup of oats, how do I calculate the hydration? I can weigh them at home (I'm not there right now, so I'm not sure how much the oats weigh), but I'm pretty sure I was using 15.5oz of flour and 10oz milk.

So if I've read other things correctly, should I be assuming milk is 90% water? And if so, is my calculation: (10 * 0.9) / 15.5, or is it (10 * 0.9) / (15.5 + weight_of_oats)? In other words, are the oats part of the "flour" part of the hydration calculation? I would assume they represent the "dry" ingredients :)

Or am I way off? :)