Just take the area of a circle times the length for the brake line.... ie pie R square for the area where pie is 3.14, R is 1/2 diameter of tube which is then squared (multiplied by itself)

A 10 foot length of brake line that is 1/4" inside diameter would go like this....
Volume=(10'x12")x(3.14x(0.125"x0.125")) [do the multiplication inside the ()s first.
Volume=120"x(3.14x0.016)
Volume=120"x0.049
Volume=5.888 cubic inches; then 1 ci =0.554 fl oz
so Volume=5.888x0.558
Volume=3.263 fluid ounce

So just plug in your length and tube diameter for the imaginary numbers I used above and you'll have it. As my high school physics teacher used to say, "I leave that as an exercise for the student!". I hated to hear that. Or as Jeff Foxworthy says; "When did they start putting letters in the formulas", when asked to help with math by one of his daughtors. grin

Oh by the way, I had to go to my trusty HP calculator to look up the cubic inch to fluid ounce conversion. I like what Einstein had to say about that; "Why clutter up your mind with facts you can look up when you need them". wink

Class of '65 too.