Only in the world of toilet paper packaging can this be mathematically true: 12=48. What these numbers really mean is that the rolls are four times larger than the smallest roll they offer. Other brands offer packages that state 6=11 or 4=12. Toilet paper math is the most convoluted and confusing math seen in our grocery stores.
I have done my best to show the calculations in the example below.
After trying several brands, Cottonelle is my favorite. To avoid having to frequently reload a new roll, I purchase the largest rolls they offer. My jumbo rolls of Cottonelle (2ply) have 284 sheets per roll. Each package of 12 rolls contains 358.8 sq ft and costs $12.48 at my local Walmart.
We are all different in our diets, elimination frequencies and the cleanliness level we seek. Forgive my disclosure of this personal information but it is necessary to show the calculations. My personal usage is 20 sheets a day. 284 sheets per roll times 12 rolls means there are 3,408 sheets per package. 3,408 sheets divided by 20 sheets a day means that a full package gives me 170.4 days of use. My cost per sheet comes to $.00366 per sheet ($12.48/3408 = $.00366). That makes my daily expenditure for toilet tissue ($12.48 /170.4 days) 7.3 cents per day or $26.64 per year ($.073 x 365). I guess I could cut back on my daily consumption but that seems like a bad idea. Maybe I should stop considering my annual toilet paper expenditure and look for other ways to save money.
Before beginning your own calculations, please note that your preferred brand and package size will likely mean different sheet dimensions and sheets per roll. Also, single ply products may require more sheets per trip to the toilet. Good luck with the math involved.