Stripline has a ground plane on both sides. Microstripline only one.
For microstripline:-

Z0 = √L/C = 377 x (t/w) x Er^-0.5

t is thickness of board, w is width of strip and Er is relative dielectric constant of material which for most PCB is between 4 and 5. I use 4.5.
50 ohm stripline is certainly about 2.8mm but micro-stripline, ie. one side of a PCB, is 6mm for about 47 ohms.
Because t/w is a ratio, you can use mm, inches or cubits if you want.
In any case, because SWR pickups are such a small percentage of a wavelength, (good readings can be obtained from 1/40 wavelength), the values are simply not critical. Plugs, sockets and solder will probably have a much greater effect.