Why a 1 TB Drive Shows Less Space in Windows

Updated 2026-10-04

A new 1 TB drive shows about 931 GB in Windows. Nothing is missing. Two number systems are being compared.

Decimal versus binary

Manufacturers count 1 TB as 1,000,000,000,000 bytes. Windows divides by 1,073,741,824, a binary gigabyte properly called a GiB, but still labels the result GB. So 1 TB becomes about 931 GB, a difference of about 6.9%.

Other space use

Formatting and the file system take a small amount. Windows features such as the page file and hibernation use more. Leaving some free space on an SSD also helps write speed.

Several drives

RAID layouts change what you can use. RAID 0 gives all capacity with no protection, RAID 1 mirrors, and RAID 5 and 6 give up one or two drives for parity. None of them replaces a backup.

Planning for games and video

Add up the installs you want and recorded footage at your bitrate. The Storage Calculator shows hours of video that fit in free space. The Download Time Calculator shows how long it takes to fill that space from the internet.