If your iPhone, iPad or Mac shows a smaller storage number than the box promised, read Apple's own explanation first. Apple publishes a support page on storage capacity, and that is the place to check how Apple reports it.
This article is short on purpose. The research behind it could not confirm why the numbers differ, the exact byte definitions, any arithmetic, or which unit each operating system uses. Rather than guess, it points you to the Apple documentation that covers the question.
Which Apple pages explain storage capacity?
This article doesn't list menu paths or a formula for each system, because its research couldn't confirm them. For Apple devices, start here:
- Apple's storage capacity support page covers how Apple devices report storage.
- On a Mac, Apple's System Information user guide is Apple's documentation for the app that shows hardware details.
Read the version of the page that matches you
Apple publishes the storage capacity page under the same page ID on several regional sites. If you're outside the US, the India version and the Europe version carry the same page number as the US one, so you can read it on your local Apple site.
The System Information guide also exists in editions for older Mac software. Pick the edition closest to the software on your Mac so the screens match what you see.
What should you do before blaming the drive?
Read Apple's pages against the figure your device shows before you assume a drive is faulty or short-changed. If the explanation there doesn't account for the gap, that's the point to contact the seller or manufacturer.
Before you get in touch, write down three things: the capacity printed on the box or listing, the exact figure your device reports, and the model of the device or drive. Having those side by side makes the conversation shorter and shows the support team exactly what you're comparing.
If you're shopping for bulk storage, How to Choose a NAS Hard Drive covers what else to check on the label.
