A foot is a foot. Fantastic. Glad to know everyone has the same sized feet.

First off, it's an estimate. Your feet don't need to be exactly 12 inches/1 foot. If your feet are only 10 inches long, it's still useful information because you know your margin of error.

That being said, there's no reason why you can't also do this trick with the metric system. You would just need to divide the amount-of-human-foot-length by around 4 to get your human -foot-measurement into meters.