Frequently Asked Questions
Getting Started
What does Fits In The Box do?
Fits In The Box is a Shopify app that uses 3D bin packing to show customers exactly how much more fits in their current shipment. It displays a shipping estimate widget on your cart page that breaks down box usage and suggests products that ship at no extra cost.
How do I install it?
Install directly from the Shopify App Store. Once installed, the app appears under Apps in your Shopify admin. Add your box configurations, sync your products, and enable the theme extension — you can be up and running in under five minutes.
What Shopify plans does it work with?
Fits In The Box works with any Shopify plan that supports the Online Store sales channel and theme app extensions. This includes Basic Shopify, Shopify, Advanced, and Plus.
Products & Dimensions
Do my products need dimensions?
Yes. The 3D packing engine needs length, width, and height for each product to calculate how items fit inside boxes. You can set dimensions in Shopify's product editor under the Shipping section, or use dimension metafields. The app syncs both formats automatically.
What units are supported?
Inches, feet, centimeters, millimeters, and meters. The app reads whatever unit your Shopify store uses and converts internally as needed.
What happens if a product doesn't have dimensions?
Products without dimensions are excluded from packing calculations. The shipping estimate widget will still work for items that do have dimensions. You can check which products are missing dimensions in the app dashboard.
Boxes & Packing
How does the 3D packing work?
The app uses a bin packing algorithm that considers all six possible orientations of each item and finds the tightest fit. It tries your smallest box first and works up. If items don't fit in a single box, it automatically splits across multiple boxes for the lowest total shipping cost.
Can I use custom box sizes?
Absolutely. You define your own box configurations with dimensions, weight limits, and shipping costs. Most merchants set up their carrier flat rate boxes (like USPS Priority Mail) but you can use any box size you ship with.
What happens if a product is too big for any box?
Oversized items that don't fit in any configured box are flagged in the shipping estimate with a clear message. You can configure how these are handled — either show a custom message or fall back to standard Shopify shipping rates.
Does it handle multi-box orders?
Yes. When a cart has more items than fit in a single box, the packing engine automatically splits across multiple boxes and calculates the combined shipping cost. Customers see a breakdown of each box and its contents.
Cold Chain & Special Handling
What is cold chain support?
If you sell temperature-sensitive items (frozen food, pharmaceuticals, etc.), the app automatically keeps them separate from ambient items. Frozen products are packed into their own boxes so you can use insulated packaging where needed.
Cart Widget
How does the shipping estimate widget work?
The widget is a Shopify theme app extension that appears on your cart page. It calls the packing API with the current cart contents and displays a real-time breakdown: which box each item goes in, how much space is left, total shipping cost, and suggested add-on products that fit with no additional shipping.
Can customers see the widget on mobile?
Yes. The widget is fully responsive and works on all device sizes. It adapts its layout for mobile screens while showing the same information.
Can I customize the widget appearance?
The widget inherits your theme's styles by default. You can also customize colors, labels, and which sections to show through the theme editor — no code changes needed.
Pricing & Plans
How much does it cost?
We offer two plans: Starter at $9/month (up to 100 products, 5 box configs) and Pro at $29/month (up to 10,000 products, 50 box configs, multi-box packing, cold chain, and priority support). Both plans include a 14-day free trial. Annual billing is available at a discount.
Can I try it before paying?
Yes. Both plans come with a 14-day free trial. No credit card is required to start — billing is handled through Shopify's billing system when the trial ends.
API & Developers
Does Fits In The Box have a REST API?
Yes. Fits In The Box provides a REST API with a full OpenAPI 3.1 specification. Authenticate with a Bearer token (fitb_ prefix) and choose between two pack modes: raw dimensions or Shopify product IDs. Interactive documentation is available at the Swagger UI.
What are the API rate limits?
The free tier includes 5,000 requests per month with a burst limit of 100 requests per hour. Pro plan customers receive higher limits. Rate limit headers (X-RateLimit-Remaining) are included in every response.
Can I use the packing API without Shopify?
Yes. The raw dimensions pack mode (POST /v1/pack) works completely standalone — send item measurements directly without any Shopify integration. Use it from any platform, custom storefront, or warehouse management system.
Where can I find the API documentation?
Full API documentation is available at multiple locations: the Swagger UI for interactive exploration, the OpenAPI spec for code generation, and our Developers page for a quick-start guide with curl examples.
Support
How do I get help?
Email us at support@fitsinthebox.com. Starter plan customers receive a response within 48 hours. Pro plan customers get priority support with 24-hour response times.