Can I limit the total pre-order units available across different variants on Shopify?

This is a common challenge if you sell the same product in multiple variants - whether that's different flavours for your food products, different varieties of your made-to-order crafts, or different sizes for your apparel. You might want to cap the total units available for pre-orders across all variants because you (or your manufacturer) can only produce so many within a time period.

Unfortunately, there's no way to set a total inventory limit across variants in Shopify yet. The platform only tracks stock per variant, not across them. Early Bird uses Shopify's inventory system to make sure your pre-order stock levels are accurate, so this is a Shopify limitation rather than an app one.

In this article, we'll go through a couple of (imperfect) workarounds.

Why this happens

Shopify tracks inventory per variant, not per individual unit inside a pack, and not across a product's variants combined.

For example, if you sell a t-shirt in 6 sizes (XS, S, M, L, XL, XXL) and set 5 units available per size, Shopify sees 6 sizes x 5 units = 30 total units available - but only because of the equal split you've set manually.

Or as another example, If you're a bakery selling cinnamon rolls in different pack sizes (1, 4 and 6) and only want to sell a maximum of 24 rolls per day, but want to sell 8 per variant:

• 8 × 1 Cinnamon Roll = 8 rolls
• 8 × 4 Cinnamon Rolls = 32 rolls
• 8 × 6 Cinnamon Rolls = 48 rolls
• Total: Shopify treats it as 88 rolls when you only wanted to sell a maximum of 24 per day.

Early Bird reads your Shopify's inventory levels to determine when to switch a live pre-order campaign to sold out, so this limitation carries through to how your Early Bird pre-order campaign behaves.

Workarounds to consider

1. Equal split across variants + Enable Back-in-stock sign-ups

Set an equal quantity across all variants that adds up to your total unit cap, run an Early Bird pre-order campaign and sell in limited quantites ("Only sell while in stock"), then enable Back-in-stock sign-ups. This way, when sold out, your variants will automatically hide the "Sold out" button and display the "Notify me when available" button instead to capture waitlist emails.

Step-by-step:

1. Divide your total unit cap equally across your variants. E.g. Using the example at the start of this article, 30 shirts across 6 sizes = 5 per size
2. Set these as the inventory levels for each variant in Shopify Admin under Products > Your pre-order product > Each variant
3. In Early Bird, create a pre-order campaign and select "Only sell while in stock" (this switches the pre-order add to cart button to sold out for a variant once its inventory hits zero)
4. Enable Back in Stock sign-ups in Early Bird

When a variant sells out, it automatically switches to a "Notify me when available" button so customers can join the waitlist - capturing their email so you can reach out when stock is confirmed. You can monitor orders as they come in and manually adjust quantities if one variant is selling faster than others.

Best for: Merchants who don't yet know the split across variants (e.g. apparel pre-orders before production begins, or baked goods with rotating flavours) and want to start capturing demand straight away.

2. Manual inventory allocation (pack sizes only)

If you sell pack-size variants like cinnamon rolls and want to prioritise larger packs first, you can work out exactly how many of each pack size equals your total unit cap, then set each variant's inventory to match.

For example, to cap at 24 rolls per day while steering customers toward larger packs:

1. Go to Products >Your pre-order product > Variants in Shopify Admin
2. Set inventory for each variant based on your unit allocation:

• 6 Cinnamon Rolls: 3 available (= 18 rolls)
• 4 Cinnamon Rolls: 1 available (= 4 rolls)
• 1 Cinnamon Roll: 2 available (= 2 rolls)
• Total: 24 rolls

1. In Early Bird, create a pre-order campaign and select "Only sell while in stock"

Best for: Merchants who know their size or pack split in advance and want to steer customers toward larger pack sizes (higher average order value).

3. Add a stock message to your product description

Add a line to your product description or storefront banner letting customers know the total units available across all variants:

⚠️ Limited pre-order: Only 30 shirts available across all sizes.  

Update this manually as orders come in. It won't prevent overselling on its own, but it sets clear expectations and adds urgency for customers to act quickly.

Best for: Any merchant, as a supporting tactic alongside Option 1 or Option 2.

4. Single variant with a custom size or flavour field

Sell your full unit cap as a single variant (e.g. "One Size" or "Mixed Pack") and add a custom text field on the product page or at checkout asking customers to enter their preference. You then fulfill based on the responses collected.

This approach works well when your split is genuinely unknown upfront - Early Bird has worked with a few bakery merchants who have used it to sell a set number of baked goods per week across rotating flavours, for example.

Best for: Merchants whose production split is entirely unknown and who are comfortable reviewing fulfillment notes manually.

Need help?

If you have questions about setting up inventory limits for your specific situation, feel free to email us at support@shopside.com.au. We're happy to walk through your store setup and recommend the right approach.