It is hard to say - so many factors. Jumps aren't uniform, all trainers teach differently and all skaters jump differently, hence it's impossible to give precise numbers on a question like this. I'll try to answer according to the techniques that my trainer taught me and that I'm teaching to my pupils.
I'd like to mention that I don't allow my pupils to think about pre-rotating on the ice at all. It misses the mark because it doesn't aid in learning the jump. Also, the answers given below are for single jumps done correctly, even expertly at high speeds - not the pre-rotation a beginner learning them or just having learned them can do or should try to do.
Why does pre-rotation on the ice occur at all? It is because all jumps are jumped in a circle, from an edge curving into the circle. The closer you get to the jump, the more rotation you create in preparation for it, and the stronger the edge curves, ending in a sort of hook before take off. That's where most of the pre-rotation of the foot/skate happens. Note that the torso may pre-rotate more than the foot, or even less, depending on the jump. The Lutz jump is the only exception - you skate in a circle/curve the other way than you are going to rotate, and pre-rotating the foot/skate on the ice is impossible. Unless you're doing it wrong.
In a salchow, the left foot usually leaves the ice 1/4 into the first revolution, still on its edge (not on its toepick) with the shoulders having done 1/2 and already facing forwards.
The toeloop is the most pre-rotated jump of all. The right foot can be as far as 1/3 into the turn, though still skating backwards, as it leaves the ice. The shoulders are about 1/2 into the turn ad facing forwards when the left toepick leaves the ice. Many beginners learn the toeloop as a waltz jump from the toe pick, that's wrong. The toe pick should only leave the ice after the right foot has skated (not swung) past it.
Now to your loop. The right foot leaves the ice about 1/5 to 1/4 into the turn. But here's the thing: the torso and hips are actually under-rotated, still facing at most forwards at take off! You did have your shoulders face into the circle before jumping, right? As to helping you do this, it's all about the curved edge you're skating on. It's probably too straight. Making their circle smaller often helps beginners.
The flip is the "straightest" of the jumps. The left foot leaves the ice almost completely backwards, at the very most 1/8 into the turn. The right toepick will turn some more, perhaps 1/4 of a revolution. The shoulders will be between backwards and 1/8.
Now the Lutz is a complete anomaly. It's very different. Beginners might first stand on their right foot and then do a loop from there, resulting in pre-rotation, but in a real lutz, where the left leg on the edge does the jumping, there is no pre-rotation. Quite the opposite: the left leg leaves the ice up to 1/8 under-rotated because of the edge curve turning in the other direction than the rotation of the jump. The shoulders will still face forwards at take off. The right toepick might get 1/8 into the turn before it gets off the ice, but still: In a single lutz you actually have to do the entire revolution, usually even more, in the air.