The most useful one in metric is the width of the open hand, from thumb tip to pinkie tip is about 20cm. It is surprisingly constant from person to person. I m

The most useful one in metric is the width of the open hand, from thumb tip to pinkie tip is about 20cm. It is surprisingly constant from person to person. I measure everything on the order of a meter with that, whether a piece of furniture will fit through a door, the size of rug I need, etc... I'm sure there are more "body measures" like this but this is the most useful to me.