The standard serving of salad dressing is two tablespoons (30 ml). That's an eighth of a cup. Two tablespoons of a vinaigrette type dressing seems like a tremendous amount of dressing to me. A thick dressing is probably not a choice if you're watching calories. How much salad dressing do people really use? How much on a side salad and how much for a salad that's a meal?
I use 1-2 tsps (5-10 ml) on a side salad and about a TBS to a tablespoon and a half (15-22 ml) on a meal salad.