Sway Bar Spring Rate

In the suspension jbeam of the 200BX and some modded cars based on it, there is a section called "torsionbars". It governs the behavior of the roll bar using a spring rate value. These values are determined by the diameter and some spring rates are given for certain diameters.

Front Sway Bar:

"torsionbars": [
["id1:", "id2:", "id3:", "id4:"],
//21mm 5277
//22mm 6356
//22.5mm 6953
//23mm 7592
//24mm 9002
//25mm 10598
//26mm 12398
//27mm 14419
{"spring":5277, "damp":10, "deform":10000, "strength":9999999},
["arbfr", "f10rr", "f10ll", "arbfl"],
],

Rear Sway Bar:

"torsionbars": [
["id1:", "id2:", "id3:", "id4:"],
//14mm 253
//15mm 333
//16mm 432
//17mm 549
//18mm 690
//19mm 857
//20mm 1052
{"spring":549, "damp":10, "deform":"FLT_MAX", "strength":"FLT_MAX"},
["arbrr", "rx2r", "rx2l", "arbrl"],
],

These sections are taken from the stock sway bars of the 200BX.

I was wondering if there was an equation to use to calculate the spring rate for the front and rear bar from the diameter or if there was an expanded table of bar diameter vs spring rate. I looked online and found calculators like this one but I do not know all of the values needed for it and Beam may calculate it differently.

 

For me, I just experiment around with different values and use the best one. I understand that this is very inefficient but it ultimately reaches my goal.