Hard drive space is the amount of digital data a drive can store. Capacity is measured in bytes and usually shown as GB or TB. The number on a drive’s label may differ from the space your computer reports or leaves available for files because of unit conventions, formatting, system data, and partitions.
What hard drive space measures
A drive’s capacity is a count of bytes. Kilobytes, megabytes, gigabytes, and terabytes are larger units used to summarize that count. Capacity is not the same as used space or free space: used space is occupied by data, while free space is what remains available within a particular volume or partition.
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How storage units work
Decimal units count in multiples of 1,000. Binary units count in multiples of 1,024 and have distinct names: kibibyte, mebibyte, gibibyte, and tebibyte. Some computer displays use the labels GB or TB for binary quantities, even though those labels formally refer to decimal units.
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| Unit | Decimal convention | Binary convention |
|---|---|---|
| Kilobyte / kibibyte | 1 kB = 1,000 bytes | 1 KiB = 1,024 bytes |
| Megabyte / mebibyte | 1 MB = 1,000,000 bytes | 1 MiB = 1,048,576 bytes |
| Gigabyte / gibibyte | 1 GB = 1,000,000,000 bytes | 1 GiB = 1,073,741,824 bytes |
| Terabyte / tebibyte | 1 TB = 1,000,000,000,000 bytes | 1 TiB = 1,099,511,627,776 bytes |
Drive makers commonly use decimal units. Seagate defines 1 TB as 1,000,000,000,000 bytes; dividing that byte count by 1,073,741,824 bytes per GiB gives about 931.3 GiB. As Seagate explains, a 1 TB drive may therefore appear as roughly 931 GB on a computer that labels binary quantities as GB. This is a unit conversion, not evidence by itself that capacity has gone missing: Seagate’s explanation of reported drive capacity and HP’s explanation of decimal and binary units provide further detail.
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- Easily store and access 2TB to content on the go with the Seagate Portable Drive, a USB external hard drive
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
Why a drive can show less usable space than its label
There are two distinct issues to keep in mind. First, decimal-versus-binary reporting changes the displayed number while describing the same byte count. Second, formatting and system data consume some storage, and existing files or partitions can leave less room available for a user’s files. Apple notes that formatted capacity is lower than the nominal capacity and that the amount reported by the operating system or apps may differ from the packaging figure: How storage capacity is measured on Apple devices (published May 21, 2024).
So the familiar 1 TB-to-about-931 GiB difference is not a complete explanation for every discrepancy. The apparent amount of free space also depends on what is formatted, reserved, partitioned, or already stored on the drive.
Quick Recap
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- [Upgraded Version] - This external hard drive features a mirrored logo stripe combined with a striped anti-slip design, and the rounded corners of the casing make it easier to grip. The stripes also have a heat dissipation function, ensuring stable and fast data transfer.
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- 【Plug and Play】 - With no software to install, just plug it in and the drive is ready to use.The hard disk chip is wrapped with an aluminum anti-interference layer to increase heat dissipation and protect data.
- 【What You Get】 - 1 x Portable Hard Drive, 1 x USB 3.0 Cable, 1 x User Manual, Gift-type shell packaging ,Three-year manufacturer's warranty and free technical support services.
Rank #4
- Easily store and access 4TB of content on the go with the Seagate Portable Drive, a USB external hard drive.Specific uses: Personal
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
Rank #3
- Easily store and access 1TB to content on the go with the Seagate Portable Drive, a USB external hard drive.Specific uses: Personal
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop. Reformatting may be required for Mac
- To get set up, connect the portable hard drive to a computer for automatic recognition no software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
Rank #2
- Easily store and access 5TB of content on the go with the Seagate portable drive, a USB external hard Drive
- Designed to work with Windows or Mac computers, this external hard drive makes backup a snap just drag and drop
- To get set up, connect the portable hard drive to a computer for automatic recognition software required
- This USB drive provides plug and play simplicity with the included 18 inch USB 3.0 cable
- The available storage capacity may vary.
How to interpret the numbers on your computer
- Compare like with like: check whether each figure is in decimal GB/TB or binary GiB/TiB. A display may use GB/TB labels for binary values.
- Distinguish total capacity from used and free space. Free space refers to what remains available in a specific volume or partition, not necessarily the entire physical drive.
- Allow for formatting, system storage, existing files, and other partitions when interpreting the amount available for personal files.
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