theres a button in the top right to switch from miles to kilometers, that does it globally and handles the calculation gracefully!
Edit: I've had my coffee now, and see what you mean. the API exposes it at /api/systems/{system}/lines/{line}, as well as aggregate for the system at /api/systems/{system}, working on supplying distance unit in api response now.
added unit type to those endpoints now.
Thank you for your effort and apologise for confusing you. English is my second language, so it might not be clear to native speakers. Thank you for adding the unit type to those endpoints! I'll enjoy your tool!