CCSS 3.MD.5A (Common Core, 3rd Grade): "A square with side length 1 unit, called "a unit square," is said to have "one square unit" of area, and can be used to measure area." The worksheets below practice this standard. Each one is a free printable PDF with an answer key, comes in multiple versions, and can also be assigned digitally - no login or account needed.
Measurement and Data Geometric measurement: understand concepts of area and relate area to multiplication and to addition.5Recognize area as an attribute of plane figures and understand concepts of area measurement.aA square with side length 1 unit, called "a unit square," is said to have "one square unit" of area, and can be used to measure area.