camera basics - Is there a formula to calculate DOF?

I am pretty clear about that DOF depends on:

1. Focal length


2. Aperture


3. Distance from subject


4. Sensor size
   and more (as pointed in the comment).

But what is the question here is: Is there any formula that relates all these factors with DOF?? Given these values is it possible to accurately calculate the depth of field??

Answer

Depth of field depends on two factors, magnification and f-number.

Focal length, subject distance, size and circle of confusion (the radius at which blur becomes visible) jointly determine the magnification.

Depth of field does not depend on lens or camera design other than the variables in the formula so there are indeed general formulas to calculate depth of field for all cameras and lenses. I don't have them all committed to memory so I'd only be copying and pasting from Wikipedia so instead I'll leave this link:

A better answer to your question would be to go through the derivation of the formulas from first principles, something I've been meaning to do for a while but haven't had time. If anyone wants to volunteer I'll give them an upvote ;)