The formulas will will drive you batty looking for the "correct" answer. There isn't one. Any formula will be inadequate because the optimum pressure will depend upon many factors including the construction of the particular tire, the weight of your rig, how and where you drive it, and personal preference.
For 33" "flotation" tires (i.e., 33x12.50R15LT), start at about 24 psi and experiment. 24-26 psi is usually right for a CJ, YJ or TJ depending upon the particular tire and the weight of the rig. My TJ Unlimited (LJ) is a bit heavier so I run my "metric 35's" at 26 psi around town and 28 on long Interstate runs.
You might try the "chalk test" with a piece of sidewalk chalk to help zero in on a particular psi, but bear in mind that the chalk is just a visual aid to make it easier to see how the tire tread contacts the ground when going a short distance in a straight line at low speed on smooth pavement. The chalk test cannot provide precise results or measure the contact patch at speed or in a turn but it is a place to start. Try it at 24 psi and go up in increments, then pick the psi with the pattern that looks best to you.