What should I do if I am using mesh coils since there is no mesh option?
Better use an ohm meter and meshure it. ? Oh no. Pardon the pun, I couldn’t help myself. Ahem.
The resistance of mesh can’t be calculated like wire, because there are so many different types of it: Different wire gauges used, different hole sizes/wire density, etc. These values are typically not standardized or stated on the package.
I don’t know if it’s even possible to model mesh coils in software without studying each and every different type and brand of mesh under a microscope, and figure out how to approximate the surface area, the wire thickness, the number of wires, and so forth and so on.
In order to implement these calculations in an easy to use calculator, the maths will have to be generalized, which is probably doable. But the base values also have to be such that the user can figure them out somehow. How else can they have actual meaningful numbers to input into the calculator? And that is the part I’m really doubtful about.
So the only practical solution that I can see, is that you measure the resistance yourself, and approximate the surface area by eyeballing it.
If you need to know the TCR, you can select a wire with the same material, and any thickness, in the Wire Wizard. The TCR will be the same regardless, as long as you don’t start mixing and matching materials.