Metric:

10 mm = 1cm, 100 cm = 1m, 1000 mm = 1m, 1000m = 1 km.

1 cm3 water = 1 gram

1 Watt heats 1 gram of water 1 C°

1 dm3 water = liter = 1 kg

1 m3 = 1000 kg = 1 tonne

Imperial:

1 mile = ?? yards = ?? feet = ?? inches

1 ton = ?? stone = ??punds = ?? oz = ?? grain

1 Galon = ?? pints = ?? fluid ounce

1 inch3 = ?? grain = ?? power to heat ?? fahrenheit

There is no system to any of these, they are unscientific and impractical.

How does Imperial still have any relevance as a measurement system?