"Calculating…" in that storage bar means Finder is waiting for the device to return its media catalog, and two things usually stall it after an iOS update.
First — check Settings > Music on the iPhone/iPad for Sync Library. If that's on, cable music sync is effectively disabled and Finder will hang on "Calculating" because there's no valid catalog to fetch. You'll usually see a small note about it under the Music tab on the device page.
Second — the bridge daemon can get stuck. On the Mac in Terminal: killall AMPDeviceDiscoveryAgent && killall AMPLibraryAgent. They respawn on their own, and the next unplug/replug usually reads the catalog cleanly. Yanking the cable while it's mid-"Calculating" can leave that daemon wedged.