petrochemist
TPF junkie!
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The longer MM a lens is, for a given distance at same aperture, the DOF for the longer lens will be thinner.
Technically this is complete garbage.
MM has no meaning here at all, what you meant I think was the Focal length which is usually measured in mm - changing the letters to caps completely changes their meaning. Technically there is a length unit of Mm, which is a megameter, 1 billion times the length of a millimeter. I never met anyone using this unit perhaps because of the ease of confusion.
Millimeters would also be suitable units for the aperture (if not measured as a ratio) and the DOF.
Your incomplete maths describes some of the aspects controlling DOF but isn't really much help.
The DOF formula is (with all distance measurements should be done in the same units):
DOF = 2 *aperture * circle of confusion * subject distance²/focal length².
Aperture being the f-stop (a unit-less number derived from the focal length of the lens divided by diameter of the opening.) not the physical diameter of the opening itself.
'circle of confusion' being the distance between two dots that the viewing system can JUST resolve - it's dependent on the viewing size but with digital systems is often taken as being the pixel size on the sensor. If the camera is kept the same it can be simply considered a constant for comparing the other aspects. Which is probably a good thing as it promotes so many technical arguments!
The other bits should need no explanation.