In the US we have a mix of:

• Price per individual unit
• Price per entire unit
• Price per weight
• Price per volume

And different products from the same category will choose different ones so you have to do the math anyway.

E.g. Sometimes our berries will be sold in split tubs so you'll get the price for the whole thing and then on the comparison tag a price for half the tub. That will be sitting next to a different brand of the same berry in a package 2oz smaller and it's comparison text will have the price per Oz, sitting next to that is an entire other brand and it will list the price of the whole unit and in comparison will list the same price again labeled explicitly as "per unit".

Like every thing the US manages to shit out it's an utterly terrible system.