What is a product's packaging size?

It is how much room one piece takes in a parcel. Pick a normal product and call it 1. Then judge everything else against it: socks might be 0,5, a winter coat 4. Set it on the variant's page, under Shipping and stock. Use the minus and plus buttons, or enter any number above 0, like 1,5.

An order adds its sizes up, and the total does two jobs. It picks the box the order ships in, if your packaging rule uses boxes of different sizes. And on a rate card that prices by size, it picks the shipping price. Two coats make 8, so they need more room than one coat.

Leave it empty, and the product counts as 1 for the box and as unknown for shipping. An unknown size sends the parcel to its zone's last price, the one for the largest parcels, and the order is flagged. Packaging size exists only in nouz, because Shopify has no such field. So a sync never changes it.

A missing size is flagged only while a box or a rate card priced by size reads sizes. Then the Weights and sizes card counts it, like 1 size missing, an empty size reads Add size in the Packaging size column, and the Filter offers No packaging size under Missing. While no cost reads sizes, nothing is flagged and the column shows a quiet dash. A product that never ships needs no size. Saving a size works the past days out again, so earlier parcels get the right box and price.