Quantity increments tell customers that they must buy in defined steps — 2, 4, 6, 8 — not arbitrary amounts. On Shopify, the cart accepts any number by default. Here is how to change that.
When You Need Quantity Increments
- Products that come in pairs (socks, gloves, earrings) — must buy 2, 4, 6
- Wholesale packs sold by the dozen — increments of 12
- Components that only work in sets — must buy in groups of the set size
- Subscription replenishments where a monthly supply equals a fixed quantity
Increment Rules vs Minimum Quantity Rules
A minimum order quantity blocks checkout below a floor. A quantity increment enforces a step pattern — every valid quantity is a multiple of your increment. They solve different problems and can be combined.
Example: minimum 4, increment 4 — valid quantities are 4, 8, 12, 16. A standalone minimum of 4 would allow 4, 5, 6, 7… which may not be what you want for a pack-sold product.
Setting Quantity Increments with Fold
Fold applies increment rules at Shopify checkout using Shopify Functions. Install from the App Store — no theme editing, no code.
Create an increment rule per variant
Target a specific variant if different sizes of the same product have different pack sizes. A 250g bag sells in 4s; a 1kg bag sells in 2s. Create separate rules for each variant.
Create an increment rule per collection
Apply the same increment across an entire collection. All products tagged ‘wholesale’ require quantities in multiples of 12 — one rule handles the whole catalogue.
Write a clear error message
Customers who enter an invalid quantity see your custom message at checkout. Be specific: “This item is sold in multiples of 4. Please update your quantity to 4, 8, 12, or similar.”
Quantity Increments for B2B Stores
B2B stores benefit most from increment rules. Pair them with wholesale minimum order rules to enforce both a floor quantity and a valid step pattern for trade customers. Use customer tag conditions to keep retail customers unrestricted.
Frequently Asked Questions
Can I set different increments for different customer types?
Yes. Add a customer tag condition: increment of 12 for wholesale-tagged customers, no increment for retail. Both rules run simultaneously.
Does it work with Shopify POS?
Shopify Functions run in the online checkout. POS quantity validation works differently.
Install Fold to set quantity increments on any Shopify product, variant, or collection.
