You can define whether you want to use metric or imperial system of measurement.
Open the Settings Editor and go to: .
Go to the [Regional settings] section.
Use the [System of measurement] setting to select the system of measurement.
[Metric]: work with g/m2 and mm.
[Imperial]: work with lb and inch.
Use the [Media weight notation] setting to select the media weight notation.
[Based on chosen system of measurement]: uses the notation as selected in the [System of measurement] setting.
[Metric]: work with g/m2.
[Imperial]: work with lb.