sentence: 1.0 mm -- 1/1000 of a metre 1.0 mm -- 0.03937 inch or 5/127 ( exactly ) 1.0 mm -- side of square of area 1 mm² 1.0 mm -- diameter of a pinhead 1.5 mm -- length of average flea 2.54 mm -- distance between pins on old dip ( dual-inline-package ) electronic components 5 mm -- length of average red ant 5.56 x 45 mm nato -- standard ammunition size 7.62 x 51 mm nato -- common military ammunition size 1 centimeter lengths between 10 − 2 m and 10 − 1 m ( 1 cm and 10 cm ) .