Costco vs Amazon: Where to Buy Diapers Cheaper in Canada
The short version
Costco's Kirkland Signature diapers usually have the lowest price per diaper of any brand we track, simply because Costco sells in bulk and Kirkland skips the brand-name marketing markup. Amazon.ca rarely beats Kirkland on price per diaper, but it wins on convenience, smaller pack sizes, and no membership fee. Which one is "cheaper" for you depends on a calculation most people never actually do.
The membership fee changes everything
A Costco membership isn't free, and diapers alone usually aren't a reason to buy one. The real question is: does what you'd save on diapers over a year, compared to buying the same total count on Amazon, cover the membership fee? If you're already a Costco member for groceries or gas, the diaper savings are close to pure upside. If you'd be joining just for diapers, do the math first — check the current membership price at costco.ca, multiply your typical monthly diaper spend by the per-diaper savings you're seeing on this site, and see if it clears the fee within the first year.
Where Amazon.ca actually wins
- No membership required — useful if you only need diapers occasionally, or are buying for a newborn who'll size up in weeks.
- Subscribe & Save stacks an extra discount on top of the listed price for recurring orders, narrowing the gap with Costco.
- Delivery — no trip, no trunk full of bulk packs, which matters more than a few cents per diaper for a lot of parents.
- Smaller commitment — Costco's bulk packs are a bad fit if you're not sure a brand or size will work out for your baby.
Don't assume — check today's actual numbers
Kirkland's price advantage isn't guaranteed on any given day — flyer sales, Amazon promotions, and stock changes shift the gap constantly. Rather than relying on a "Costco always wins" rule of thumb, compare the live price per diaper for both retailers below.
See today's Costco prices See today's Amazon.ca prices