Frequently asked
Where the shipping rates come from, whether your data leaves your browser, why CartonFit doesn't quote freight, and what the tool deliberately leaves out. Short answers, no sales pitch.
The workbench is free while in beta and the three calculators are free, always, with no signup. A paid tier is planned; the free calculators will stay free.
The bundled rates are public list prices, each labeled with a source and a scope. They are not quotes and they go stale — the numbers that matter are the ones you type in from your own forwarder, and the whole comparison re-runs on your numbers.
No. Every number is computed locally. Nothing is uploaded, there is no account, and your edits persist in your browser's local storage. The only data CartonFit ever receives is an email address you explicitly submit to the release notification list.
Because a comparison is only honest when every line is comparable and current. Quotes expire and hide their scope. CartonFit compares channels on the rates you supply and stays out of the freight-selling business entirely.
No, and this is stated up front rather than buried. Duty, tariffs and de minimis rules change too often to belong in a yes/no comparison, and they don't affect how you should pack a box. Port-to-port and DDP options are labeled with their scope so they are never compared as if equivalent.
Express, air freight, LCL and FCL, priced side by side on the same carton plan. Each line shows what it bills on, its chargeable units, and its scope; channels that physically cannot carry the shipment are listed with the capacity reason rather than silently dropped.
The tier table carries the date it was verified against Amazon's published seller help pages, and the underlying data file includes a verification log. The current table includes the Small Bulky tier introduced with the January 2026 fee changes.
One SKU per carton, no soft-pack compression, no invented carton sizes, no duty modelling — each disclosed on the workbench page. A tool that hides its limits gets used past them.