You're thinking about it wrong. 2 feet is about 600mm or 60 cm or 6 decimeters or 0.6m or 0.06 dekameters. Just pick whatever prefix that gives you the number

You're thinking about it wrong. 2 feet is about 600mm or 60 cm or 6 decimeters or 0.6m or 0.06 dekameters. Just pick whatever prefix that gives you the number of significant digits you want. Metric doesn't "lack units", because there's only a single unit for every measure. Instead there's prefixes for every power of ten around human-scale measurements, and for every power of thousand for much smaller and much larger measurements.