Shipping & customs6 min read
Shopify Packed Product Size: How Shopify Picks the Box
What Shopify's packed product size does, when Shopify packs an order into your smallest saved box, when it falls back to the default package, and how to fill it in.
In this guide
For years the answer to “how does Shopify know which box an order ships in?” was: it doesn’t. Every multi-item order was rated with your store default package, so a cart with one mug and a cart with six mugs were priced as if they shipped in the same box. A lot of advice online still says that.
It is no longer the whole story. Shopify now has a packed product size field on each product and variant. When every item in a shipment has one, Shopify can pack the shipment into the smallest of your saved boxes that fits. This guide explains what the field does, when Shopify uses it and when it falls back to the default package, and the three ways to fill it in without an app.
What packed product size is
Shopify’s help center defines it as “the outer length, width, and height of a product after it’s packed” (Setting up packages). It is not the size of the product itself. A mug that measures 9 × 9 × 10 cm but ships wrapped in bubble wrap might have a packed size of 12 × 12 × 11 cm.
The field sits in the Shipping section of a product, or of each variant when the product has variants, next to the weight. Two rules from the help center:
- All three or none. You must enter the length, width and height, or leave all three blank. If you enter only one or two, the packed size is not saved.
- Physical products only. The product has to be set as a physical product.
How Shopify uses it
According to the same help page, “the items in each shipment are packed into the smallest of your saved boxes that fits them”, and if an order ships from several locations, the items from each location go into a separate box. The aim is more accurate carrier-calculated shipping rates at checkout.
Your box’s weight still counts. Shopify adds the package weight to the weight of the products, so a heavy box can move an order into a higher weight-based rate. That makes the variant weight just as important as the three dimensions.
When Shopify uses the default package instead
The help center lists the cases where Shopify falls back to your store default package for a shipment:
| Case | What to check |
|---|---|
| Any product in the shipment has no packed product size | Fill in every variant that ships, not only best sellers |
| Your default package is not a box | Make a box your store default package |
| None of your saved boxes fits the items | Add a larger box, or accept the fallback for oversized orders |
| You have a large number of saved boxes | Keep a short list of boxes you really use |
| The order has a large number of items | The more boxes you save, the fewer items an order can have before this happens |
Only packages of the Box type are picked this way. Envelopes, soft packs, flat rate packages and carrier packages are not. Shopify does not publish exact numbers for “a large number” of boxes or items, so test with your own carts.
A single-item order works differently. If you picked a package in a variant’s Package when shipped alone menu, that package still takes priority for an order of just that item. Shopify’s changelog introduced that per-variant default package in 2025, for single-item orders (Shopify Changelog).
Three ways to fill it in without an app
1. On the product page. Open the product (or the variant), go to Shipping, enter the length, width and height under Packed product size, choose the unit and save. This is fine for a handful of products.
2. In the bulk editor. Shopify’s help says you can add a packed product size to variants in bulk with the bulk editor. Select the products, click Bulk edit, then add the columns you need with Columns (Bulk editing products). You can drag a cell’s fill handle to copy a value down a column.
3. With a product CSV. The product CSV has the columns Packed product length, Packed product width, Packed product height and Packed product dimension unit (cm or in) (product CSV column reference). Export your products, fill the four columns, and import the file again. Try it on a few products first.
Which one to use is a matter of catalogue size. Our guide to bulk editing weight and packed dimensions compares the bulk editor and CSV in more detail.
A checklist before you rely on it
- Save the boxes you really use in Settings › Shipping and delivery › Packages, as Box packages, with their outside dimensions and empty weight.
- Make a box your store default package, so the fallback is at least a realistic box.
- Give every shipping variant a packed size and a weight. One variant without a packed size sends the whole shipment back to the default package.
- Start with the variants that sell. A complete catalogue is the goal, but the orders you ship this week come first.
- Test a few carts at checkout: one item, two small items, a mix of small and large. Compare the rates with what you expect from the box you would use.
If you are still choosing which boxes to save, our guide on how to choose shipping box sizes starts from your orders.
The hard part: finding the gaps
With twenty products, step 3 takes an afternoon. With a few hundred variants, the question becomes “which ones are still missing?”, and Shopify’s product list does not show you that at a glance. Because one missing variant is enough to send a shipment to the default package, the gaps matter more than the averages.
FAQ
Does Shopify use packed product size for every order?
No. Shopify uses it when every item in a shipment has a packed size, your default package is a box and one of your saved boxes fits. Otherwise the store default package is used. For a single-item order, a package chosen under Package when shipped alone takes priority.
Is packed product size the same as the product’s dimensions?
No. It is the outer size after packing, including wrapping or a retail box. Product dimensions you show on the product page are usually kept in metafields and are not used for shipping.
Can I import packed dimensions with a CSV?
Yes. Shopify’s product CSV has columns for packed product length, width, height and dimension unit. Fill all three sides or none.
Do I need packed dimensions if I use flat-rate shipping?
Packed product size is about carrier-calculated rates and choosing a box. If all your rates are flat, the box choice does not change what the buyer pays at checkout, though accurate weights and sizes still help when you buy labels.