How do you say ‘about a foot’ in metric?

Don’t get me wrong, I love the precision and scalability of the metric system, but what if I don’t want precision?

“About a yard long” becomes “about a meter long,” no problem.

“A few miles” becomes “several kilometers,” no problem.

“About a foot long” becomes . . .

  1. about 30 centimeters? (sounds too precise)
  2. about a third of a meter? (avoid fractions)
  3. approximately three decimeters? (deci-what?)
  4. about as long as a person’s foot? (man or woman? what shoe size?)

I’ve wrestled with this problem long enough. Don’t be surprised if the aliens in my metric-system-based stories have arms, legs, antennae, and reproductive organs about a meter long!