How much vitamin d is in milk?

Vitamins are measured in "international units."

RAW MILK contains approximately 40 IU (international units) per liter. Pasteurized, fortified, reduced fat milk, specifically 2% milk, contains about 105 IU a cup -- which works out to a little over 443 IU every liter.

Sources:

http://nutritiondata.self.com/facts/dairy-and-egg-products/71/2

Self Magazine

http://jn.nutrition.org/content/112/4/667.full.pdf

LORRAINE E. REEVE, NEAL A. JORGENSEN" AND HECTOR F. DELUCA2

Departments of Biochemistry ir 'Dairy Science, College of
Agricultural and Life Sciences, University of Wisconsin-
Madison, Madison, Wisconsin 53706