A pretty common approach (at least in Canada) is to use prefixes at intervals of 1000 - mm, m, km and then larger unit to one decimal for large values - 700m as

A pretty common approach (at least in Canada) is to use prefixes at intervals of 1000 - mm, m, km and then larger unit to one decimal for large values - 700m as 0.7km, 0.9l instead on 900ml, and so-on. you'll rarely see cl, dg, or hm used here.