This was really frustrating when I had to be price sensitive shopping for paper towels. They'd list price per roll in the corner of the tag, but every package's rolls were significantly different cm^2 quantities.
It's a hard problem. Some stores have half-size paper towels, which I prefer, as paper towels are unnecessary large most of the time. So I want to price-compare based on number of sheets, not cm² ;)
I have the same issue with rice, they always put the price per kg, never per grain..
weight is better for rice since individual grains will vary with size and width.
That's the point, I would only take the biggests.
I only want that until someone figures it out and starts making 1/100 size sheets, or some other cheat.
I just rip off the size of paper towel I need every time I use them.
They're not half-size, though, they're actually a bit _more_ than 50%. So that means you'll go through them faster than if you purchase full-sized ones and get in the habit of tearing a full sheet in half and setting the unneeded half aside.
All of my grocery shopping is done on my supermarkets website and sorting by unit price brings up the price per pound or ounce or whatever that products unit of measure is. For paper towels it returns $ per square foot, so even if the product size is different the price per unit of measure stays the same and makes it easier to comparison shop.
It's the same for toilet paper. We really need sane regulations on packaging to make it easier for consumers.