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Costco’s $5 rotisserie chicken is definitely one of its most iconic deals. It’s right up there with maximizing purchase rewards as a solid way to save money at Costco. (We can get two to three family dinners out of one chicken in our house.)

But as famous as it may be, it’s not actually Costco’s best-selling product. No, the item with that distinction is somehow even more mundane than chicken.

Kirkland Signature toilet paper is reportedly the top seller

It may not be glamorous, but it sure is pulling in the sales. Which makes sense when you think about it; as the book says, Everyone Poops.

And boy howdy, everyone must be doing a lot of it. Reports suggest that Costco sells more than a billion (that’s nine zeroes, for those keeping score) rolls of Kirkland toilet tissue per year, totaling upward of $400 million in sales annually.

Part of Costco’s winning formula is to combine price, quality, and convenience, which it certainly achieves with this product. Let’s break it down.

Comparing Kirkland TP on price

Costco’s TP sales numbers are even more impressive when you consider that Kirkland toilet paper is about as low-cost per-unit as you can buy (before you hit rest-stop tracing paper…).

For comparison, let’s look at how it stacks up against Charmin (also sold at Costco) and rival Sam’s Club’s Member’s Mark house brand:

There is no standardization in sheet or roll sizes for toilet paper, so we used price per square foot to get the most apples-to-apples comparison. By this metric, you’re paying more than twice as much for the brand-name Charmin toilet paper even if you buy it in bulk sizes from Costco. It also beats out Member’s Mark by a not-insignificant margin.

Pro tip: Make sure you’re using your best Costco rewards credit cards every time you restock on TP, paper towels, and all your other household essentials.

Comparing Kirkland TP on quality

While price is easy to compare objectively, we all have different preferences, so quality comparisons will depend on the bum of the beholder.

That said, I looked at reviews for all three brands, and Kirkland Signature certainly holds its own. However, Costco shoppers actually prefer Charmin Ultra Soft, and Sam’s Club reviewers give Member’s Mark a near-perfect score:

Comparing Kirkland TP on convenience

In addition to saving money, buying shelf-stable staples in bulk has another big advantage: fewer shopping trips. If you hate changing the toilet paper roll and going to the store, then buying super-duper-mega rolls in a gazillion-pack is ideal.

Kirkland Signature is pretty much there. Not only are the rolls larger than other brands, but you get a large number of them. Kirkland wins hands down in sheer size:

Studies suggest the average person uses about 13,000 sheets per year, which would be around 34 rolls of Kirkland Signature bath tissue. The same person would require around 56 Member’s Mark rolls and 57 Charmin rolls.

Your bum — and budget — could do worse

No matter how you look at it, Costco’s best-selling toilet paper is a winner for a reason. You get an excellent price, competitive quality, and rolls large enough to get you through the next TP shortage. Consider giving it a try on your next Costco run.

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We’re firm believers in the Golden Rule, which is why editorial opinions are ours alone and have not been previously reviewed, approved, or endorsed by included advertisers.
Motley Fool Money does not cover all offers on the market. Editorial content from Motley Fool Money is separate from The Motley Fool editorial content and is created by a different analyst team.Brittney Myers has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Apple and Costco Wholesale. The Motley Fool has a disclosure policy.