Why a new drive shows less storage than you paid for
The gap between a drive's advertised capacity and what the operating system displays mostly comes from different counting systems and from pre-installed software taking up space.
Buyers of internal or external drives often notice that their computer shows less usable space than the product promised. Technology site Engadget explains that this is usually not an attempt to cheat customers, but the result of different calculation methods and system requirements. The issue matters more now because storage is getting pricier: the article says demand from AI datacenters is pushing up drive prices, and companies such as Apple and Valve have raised the prices of some products by hundreds of dollars.
Decimal versus binary
Storage makers commonly calculate capacity in the decimal system, where a kilobyte is 1,000 bytes and a gigabyte is 1 billion bytes. Software platforms such as Windows often measure in binary, where a kilobyte is 1,024 bytes and a gigabyte is 1,073,741,824 bytes. The larger the figures, the wider the gap. A 1TB drive may appear as 931GB in Windows even though nothing is lost, while a Mac, which uses decimal, shows the full 1TB. As an example, the article cites a 512GB drive that registered only 477GB as accessible to Windows.
To Engadget's knowledge, Microsoft does not plan to switch Windows to decimal, and Apple is not planning to return its products to binary. Binary-specific terms such as "kibibyte" (KiB) and "gibibyte" (GiB) have not caught on, and Windows 11 still displays file sizes as KB or GB.
Space taken by the operating system
Another cause is the pre-installed operating system. The article says iOS 27 uses over 22GB (decimal) on a 128GB iPhone 16 Pro, and Windows 11 occupies over 81GB (binary) on one of the outlet's gaming laptops. Operating systems tend to grow each year, and devices also need extra cache and swap space for temporary files. If that space is not protected, downloading too many files or apps can hurt performance and lead to apps freezing or crashing.
The author advises using storage conservatively and overestimating how much capacity you need when buying.
