How to read voltage ratings of wire

I notice that some vendors and suppliers just list a voltage rating w/o specifying whether it is DC or AC, unlike others.

From other places it appears, wires can handle much less AC voltage than DC voltage ( I am guessing b/c AC is usually express in RMS than peak or peak to peak.)

So, I would think by roughly treating the VDC as a peak to peak I should get the following:

Vac = 0.3535 * Vdc

However based on some wires that have both Vac and Vdc spec, I am getting more like 0.44 b/t the two.

Are my assumptions wrong? I know it is not a true since wave, but I figure close enough.

Voltage rating of a wire is about the insulation, and that reacts differently to AC or DC. A DC voltage is actually worse case for some insulation materials, as a steady DC voltage can cause ion migration through the insulation and failure, at a lower voltage than the AC.

Take the ratings as listed, don't try to rationalize them.

the voltage rating of wire is really a rating of the insulation surrounding it not the conductors,f you need the peak of ac multply by 1.414