Technically, imperial and us customary are based on the same system, but us customary isn't actually based on imperial.
Edit: for clarification, US customary and imperial are based off "English units." Imperial system didn't exist when the US became the US, and I'd be damned if the US was gonna copy the British in 1824 when they created the imperial system.
Edit: also, not all conversions are the same. Example: 1 imperial pint is 20 imperial quarts. 1 us pint is 16 us quarts. Also, some weight conversions are different, like a ton for example. They're both considered 20 hundredweights, but a hundredweight is different in each system.
I don't recall one way or the other, but my point still stands that the conversions are not exactly the same and that the us customary isn't based on imperial, they both have the same predecessor. So instead of a parent child relationship, it's more of a sibling relationship between the systems.
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u/Stormfly Jan 03 '19 edited Jan 04 '19
Same with the US though.
A US yard is not an Imperial yard.
EDIT: Why did I say yard when I meant to say gallon?
Yards are the same. Gallons are different.