Not as part of the comparison, and the reason is worth understanding, because it’s structural rather than a setting anyone left out.
FedEx One Rate is flat-rate shipping: a fixed price for packages up to 50 lbs that fit into specific FedEx-branded packaging, regardless of distance within the US. The weight allowance is generous, so it can be very cost-effective for heavy items that fit the preset dimensions — FedEx Pak, FedEx Box, FedEx Envelope and the rest.
Eligibility for One Rate depends on packing into FedEx’s box. That makes it a packing question before it is a pricing question.
Rate shopping runs the other way round. A rate shopper takes the package as an input and finds the best service for it — ShipStation’s own setup documentation has the dimensions rule running before the Rate Shopper rule for exactly this reason. By the time rates are fetched, the box is already decided. If you packed into your own carton, One Rate was ruled out before anything was priced.
So the two decisions have a circular dependency:
That’s a joint decision, and no sequential tool solves a joint decision by doing one step and then the other. The same is true of USPS Priority Mail Flat Rate, and it isn’t specific to ShipStation — it follows from rating happening downstream of packing. The full explanation is here.
If One Rate is a small share of your volume, the usual answer is to handle it as a separate rule rather than expecting the comparison to find it: identify the order profiles that reliably fit a One Rate box and set them explicitly.
If it’s a meaningful share, the decision has to be made jointly — price the order against your standard rates and against each flat-rate box’s constraints at the same time, and take whichever comes out cheaper. That’s the calculation we build alongside ShipStation for operations where the packing and the rate can’t be separated.
Knowing how a carrier prices a package is useful. The harder problem is making the right packing and rate decision on every order, when the correct answer changes with the contents, the destination and the rate card.
String builds and maintains that logic inside existing ShipStation accounts, for operations shipping roughly 6,000 orders a month or more. Below that, ShipStation's native automation and accurate product dimensions will get you most of the way there.
Eight patterns that show up when an operation needs custom shipping logic
