No, the gram is used for small weights, even though the gram is a mass unit, not a force unit or weight unit.
The SI (metric) unit for mass is the kilogram.
No mililimeter can weigh a gram. A gram is a metric unit of weight, and a millimeter is a metric unit of length or distance.
The gram is a metric unit of mass.
A gram is a metric unit of mass. Ounces are not metric. Ounces might be a unit of weight, but they might also be a unit of liquid volume, and you have to guess which one is intended, because they're not equivalent. Also, a fluid ounce in the US is not the same as a fluid ounce in the UK, but a ounce of weight in the US is exactly the same as an ounce of weight in the UK.
A "gran" is a German measurement, it is neither customary or metric. A "gram" is a metric unit.
A litre is a metric unit of volume.
It appears that you don't understand that the unit 'gram' IS a metric unit used to quantify the mass, or more conventially, the weight, of an object.
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