I use a fine mark steel ruler.
millimetres (or tenths of millimetres, if you have a micrometer)
Centimetres and millimetres.
You can use a ruler or a measuring tape to measure the length of a fish in a bowl. Place the measuring tool along the straight body of the fish from the tip of its nose to the end of its tail to get an accurate measurement.
You can use a measuring tape, a ruler, or a yardstick to measure your height.
Scale
steel rulemeasuring tapelaser measuring deviceruleyardstick...
mgs
A theodolite.
Millimetres.
measuring tape
Caliper. Micrometer
millimetres are just a more accurate form of measuring length. Most designing work used millimetres in order to be more precise about how big you cant things. In the sciences (mainly physics) many things are measure in mm.