What is a nonstandard unit?

A nonstandard unit is a unit of measure expressed in terms of an object such as a shoe, toothpick, paper clip or stick of gum, according to the Catholic School Department Diocese of Sacramento. It can also be expressed in informal terms such as a hand span or body length.

Nonstandard units are typically used when initially introducing young learners to various attributes and concepts involving measurement. These concepts include more of and less than, measuring by laying objects end to end, sorting and classifying into categories according to size, comparing the lengths of two objects by using a third, describing objects in terms of relative size, and ordering objects by length.