Coach- Length: centimeter (cm) for small things, meter (m) for big ones, with m cm;
- mass: gram (g) for light things, kilogram (kg) for heavy ones, with kg g;
- capacity (how much a container holds): liter (L).
Smaller units and their exact rules come in Chapter 19.
Examples
Example 12.2 (Which unit?)
A crayon: about cm. A door: about m. An apple: about g. A big bag of flour: kg. A milk bottle: L. Guess the unit before measuring — it stops silly answers like “the door is cm”.