2002 Subaru Outback Brake system capacity

What do you mean by capacity? Amount of total brake fluid or how much load the brakes can handle as in trailer capacity/load?

Sorry, I should have clarified that. I mean the fluid capacity. I need to replace it's brake fluid and I have some good stuff left over from another job.

Capacity of the system doesn't mean much since you bleed until the fluid is clear. So it's an "as needed" item.

The times I've done the Outback Murphy's law prevailed, with me needing a small can and a tablespoonful from another one. (:

I usually start with two small unopened cans of dot 3/4 and end up with ~ 1/2 can after a complete flushing.