Is Costco better than Amazon for baby diapers?

Whether Costco or Amazon is better for baby diapers depends on what you value most: lowest unit price, convenience, or brand selection.

Costco is often the better value if you have a membership and can buy in person.
Costco’s Kirkland Signature diapers are generally regarded as a strong store-brand option, and Costco often has competitive price-per-diaper pricing in the warehouse. The tradeoff is that selection is usually narrower, and the big boxes can be inconvenient to haul home. Costco’s online prices can be different from in-warehouse pricing, so it’s worth comparing the final delivered price.

Amazon is usually better for convenience and variety.
Amazon typically has a much wider selection of brands and sizes, plus fast delivery. Its Subscribe & Save program can reduce diaper costs, but the exact savings and eligibility can vary, so check the current offer before relying on it. For busy parents, the biggest advantage is often the ease of automatic doorstep delivery.

Bottom line:

• Choose Costco if you want strong value and are happy with a simpler diaper selection.
• Choose Amazon if you want convenience, more brand choices, or automatic delivery.

Best practice: compare the price per diaper after taxes, shipping, membership fees, and any subscription discounts. That matters more than the box price, especially because diaper counts and prices change by size.