After adding unit groups, continue by adding new units.
These units will be displayed next to the product fields in the product page.
Choose the unit name, symbol, group and the conversion ratio in relation to the default unit of the selected group.
New unit = Conversion ratio x Default unit.
Here’s an example with Centimeter as the default unit in the group Length:
You can make a unit as the default unit in its group either by clicking this icon
Or by editing the unit group and changing the Default Unit value