Metric system is very sensible Spacey. Kilo = 1,000. So kilometre is 1,000 metres. 0.6 km would be 600 metres, 0.06 would be 60 metres, 0.006 would be 6 metres.
None of this inch/foot/yard/furlong/cubit/mile nonsense. All you need are millimetre, 1000 of them = metre, 1000 of them = kilometre. Now you can measure everything (except for very small distances - micrometre - or very large distances - light years / minutes / seconds).