Selling in multiples means your customer can only buy 2, 4, 6, 8 — not 3 or 5. It is essential for products that come in pairs, sets, or standardised packs. Shopify does not include this natively — here is how to add it.
Products That Sell in Multiples
- Pairs — socks, gloves, cufflinks, earrings (must buy 2 or 4, never 1 or 3)
- Sets — placemats, chairs, glasses (must buy in the set unit)
- Case packs — beverages, packaged food sold by the tray or box
- Component kits — screws, dowels, or fittings sold in standardised counts
Selling in Multiples vs Quantity Increments
“Selling in multiples” and “quantity increments” describe the same mechanic — both mean the quantity must be a multiple of a defined number. The terms are interchangeable. Both use Fold’s increment rule.
How to Set Up Multiple-Based Selling on Shopify
Fold uses Shopify Functions to enforce multiples at checkout. Install from the App Store.
For a pairs product
Target the product. Increment = 2. Valid quantities: 2, 4, 6, 8. Error message: “This product is sold in pairs. Please add 2 or a multiple of 2.”
For a case-pack product
Target by product tag. Increment = 12. Valid quantities: 12, 24, 36. See also: how to sell in case packs on Shopify.
Combining with a minimum
Set minimum = 2 and increment = 2 for a pairs product. The minimum prevents single-unit purchase; the increment prevents 3-unit or other odd-number orders.
How Customers Experience the Rule
Shopify’s cart allows any quantity. The rule validates at checkout — not at the cart stage. When a customer tries to proceed with an invalid quantity, they see your custom error message and must correct their cart before paying.
Frequently Asked Questions
Can I show a hint in the product page before checkout?
The checkout validation is mandatory. Adding a product page note (“Sold in pairs — please add in multiples of 2”) is a good UX addition but not enforced. The Fold rule at checkout is the guarantee.
Can I target specific variants for multiples?
Yes. Different variants of the same product can have different increment rules. A 250ml variant sells in 6s; a 1L variant sells in 2s.
Install Fold to force customers to buy in multiples on Shopify — pairs, sets, case packs, or any increment.
