The board thicknesses are given in mm so it is not clear that the required units for trace width appear to be mil (0.001 inch). It would be nice to have a mm/mil switch including the board thicknesses.

@martin, Why do you expect to see frequency in a trace impedance calculator? The type of calculator offered by JLCPCB is to calculate characteristic impedance of (a limited set of) PCB transmission line structures. To first approximation, transmission line impedance is independent of frequency. As the signal frequency increases losses in the dielectric (substrate) and copper (skin effect and surface roughness) increase but the characteristic impedance is more or less constant. If the signal frequency is so high that all the above effects start to matter then you should not be relying on a simple calculator but should be using tools like MWI: [http://blog.rogerscorp.com/2018/07/12/calculate-microwave-impedance-with-transmission-line-modeling-tool/](http://blog.rogerscorp.com/2018/07/12/calculate-microwave-impedance-with-transmission-line-modeling-tool/) or a multi-layer dielectric field solver tool such as mdtlc: [http://mdtlc.sourceforge.net/](http://mdtlc.sourceforge.net/) If you want to calculate the complex impedance of a given trace at a specific frequency for example if you want a piece of track to present a given impedance to an RF power amplifier or as part of a filter then a PCB transmission line calculator is the wrong tool because that is not what they are set up to do.

@andyfierman, I will plainly admit a brainfart. Chalk it up to too many Smith chart antenna match calculations! 

Hello ; Considering your post " I am not sure how it's supposed to work " Since JLCPCB produces high precision PCBs then every single parameter should be controlled carefully and that's why we are providing this guide calculator to define what is the trace width and trace space to set in order to maintain a certain impedance value. If you explain your requirement then we can better help you to find the right place for searching :) Thank you for making your post here.

@jlcpcbsupport Hi! Sorry, please feel free to ignore me at this time!