Live Rates at Checkout
USPS and FedEx each register as a standard WooCommerce shipping method, so customers see real carrier pricing at checkout instead of a flat estimate.
Enable the carrier
Enter credentials and enable USPS and/or FedEx under their settings tabs first.
Open Shipping settings
Go to WooCommerce → Settings → Shipping.
Add the shipping method
Open a shipping zone, click Add shipping method, and select USPS and/or FedEx.
Configure per-zone filtering and markup
Choose which services are offered in this zone, and set an optional markup (flat amount or percentage).
Rate Caching
Live rate lookups are cached for 30 minutes per unique cart (weight, dimensions, destination) to avoid calling the carrier API on every checkout page load.
Rates use the same auto-calculated package weight/dimensions as label generation. If a product is missing weight or dimensions, add them in the product editor - carriers reject rate requests for packages with no size.