Is Costco worth it for formula and diapers?

Usually yes—Costco can be worth it for formula and diapers if you can actually use the bulk quantities and you shop there often enough to offset the membership fee.

Typical savings (very approximate):

• Diapers: about $20–$45 per bulk box vs comparable name-brand retail pricing, depending on size/brand and promos.
• Formula: about $5–$20 per container versus mainstream retail, with the biggest savings when Costco carries the exact formula you already use.

A few practical notes:

• Diapers: Costco is often a strong value, especially for Kirkland Signature diapers if they fit your baby well. Fit and leak performance matter more than small price differences.
• Formula: Costco can be worth it if your baby tolerates Kirkland formula or Costco has a good price on your preferred brand. Don’t switch formulas just to save money without checking ingredients and getting medical guidance for sensitive needs.
• Membership math: If you also buy wipes, paper goods, groceries, or gas there, the membership is easier to justify. If you’re only buying baby items occasionally, the savings may be too small.

Caveat: prices and pack sizes change often, so check current shelf prices and sold/completed listings before deciding.