Box suggestions in the Shipit Shopify Delivery Checkout

This feature automatically calculates how many boxes you need, and what size, based on the boxes and items you have available. You don't need Carrier Calculated Shipping (CCS) to use it.

1. Turn on the feature

Go to Settings > Automation > Parcel Weight Settings.

Under Parcel weight preference, select Shopify order weight. Box suggestions only work when this is selected, if the parcel settings weight is used instead, the feature won't work. Note that this is a global setting and cannot be overridden by individual parcel settings.
Check "Suggest boxes during manual shipment creation". This calculates parcel dimensions and gross weight from the selected order items and any manual extras. Suggestions are always reviewable before booking.

2. Set up your boxes for suggestions

Boxes are managed on the Parcel settings page, found in the app menu under Apps > Shipit Delivery Checkout > Parcel settings.

Create a new parcel setting or edit an existing one. Fill in the name, length, width, height, and type. The regular weight field isn't used for suggestions, the relevant fields are the empty box weight and maximum gross weight, covered below.
Check "Use this parcel as a candidate box" under Box suggestion data. A parcel marked this way can be suggested on the Create Shipment page, but only when it's also assigned under Shipping method availability for the shipping method used on that shipment.
Once checked, the app automatically fills in estimates for a standard single-wall cardboard box: inner length, inner width, inner height, empty box weight, and maximum gross weight. Click "How estimates are calculated" for details:

Inner dimensions subtract 0.5 cm per side, empty weight is estimated from the cardboard's surface area, and maximum gross weight is based on the weight threshold plus tare, or defaults to 10 kg.
Always verify every value, especially empty box weight and maximum gross weight, since these are what the suggestion calculation actually relies on. Documents and pallets require manual values, they aren't estimated.

You can optionally add clearance per side if you want to leave extra room for packing material.
The same form also shows the available contents capacity (maximum gross weight minus empty box weight), so you can see at a glance how much weight the box can hold.

3. Get a box suggestion when creating a shipment

Go to the order's Create Shipment page and scroll down to the Parcels section:

If there are multiple fulfillment groups on the order, you'll need to select which one you're creating the shipment for.
If any product is missing dimensions or weight, the app will ask you to fill them in, you can also save these values for future orders so you won't need to enter them again.
If the shipment includes items not found in the Shopify order data (e.g. gifts or packing materials), add them using "Add manual item". Fill in the description, quantity, dimensions, and weight. You can also choose:

Category: "Packing material" or "Shipment content", depending on whether it's a sellable product or e.g. padding or other packing material. Note that shipment content isn't added to customs declarations, so it can't be relied on for international box suggestions.
Rotation: "Best fit", "Keep flat", or "Do not rotate" — this controls how the item is allowed to be oriented in the calculation.
"Ship separately": if the item shouldn't be packed together with others in the same box.

If you add the same item often (e.g. a sample, gift card, or standard packing material), you can save it as a preset by clicking "Save as reusable preset" after filling in the details. Next time, you can select the item directly from the "Reusable extra item" dropdown and click "Add preset" — the item is added automatically to the form without needing to fill it in again.

Click "Estimate boxes". The app calculates the boxes needed based on the order items and any added items.
The suggested boxes and their dimensions/weights are automatically copied into the parcel cards below. Review and edit as needed before booking, nothing is booked automatically. If you change any inputs after estimating (items, quantities, dimensions, etc.), click "Estimate boxes" again to refresh the suggestion.
Clicking "Save" at the top of the page actually creates the shipment, and then opens the label download flow.