What is a terabyte?
A terabyte (TB) is a unit of digital information storage used in computing. Depending on the context, it can represent two distinct values:
- SI (International System of Units) Definition:
- 1 TB = bytes = 1,000,000,000,000 bytes.
- This system uses base-10 prefixes (e.g., kilobyte, megabyte, gigabyte).
- Binary (IEC) Definition:
- 1 tebibyte (TiB) = bytes = 1,099,511,627,776 bytes.
- The binary system, standardized by the International Electrotechnical Commission (IEC), uses base-2 prefixes (e.g., kibibyte, mebibyte, gibibyte).
Confusion arises because many operating systems and software tools historically used binary prefixes but labeled them with SI names (e.g., reporting bytes as “TB”).
Understanding data measurement units
SI (Base-10) system
- Kilobyte (KB): bytes.
- Megabyte (MB): bytes.
- Gigabyte (GB): bytes.
- Terabyte (TB): bytes.
Binary (Base-2) system (IEC standard)
- Kibibyte (KiB): bytes.
- Mebibyte (MiB): bytes.
- Gibibyte (GiB): bytes.
- Tebibyte (TiB): bytes.
Key distinction:
- SI units are used by storage manufacturers (e.g., “1 TB SSD”).
- Binary units are used by operating systems (e.g., Windows reports 1 TB as ~931 GiB).
Formula
Converting TB (SI) to bytes
Converting TiB (IEC) to bytes
Examples
Example 1: Converting 1 TB (SI) to bytes
Example 2: Converting 2.5 TB (SI) to bytes
Example 3: Converting 1 TiB (IEC) to bytes
Practical use case: A video production company stores 10 TB of raw footage. In bytes, this equals:
Notes
- SI vs. IEC standards: Always verify which system is being used to avoid errors.
- Operating systems: Windows uses binary units but labels them as SI units (e.g., “TB” instead of “TiB”).
- Storage marketing: A “1 TB” hard drive marketed using SI units will display as ~931 GiB in Windows.
- Precision: For exact calculations, use .
Frequently Asked Questions
How many bytes are in a TB?
In the SI system:
In the binary system:
Why does my 1 TB drive show only 931 GB?
Storage manufacturers use SI units ( bytes), while operating systems use binary units:
This discrepancy is due to the difference between base-10 and base-2 systems.
How to convert 5 TiB to bytes?
Using the IEC formula:
Are TB and TiB Interchangeable?
No. A terabyte (TB) is bytes, while a tebibyte (TiB) is bytes. The difference grows with larger units (e.g., 1 TB ≈ 0.909 TiB).
What is the historical reason for two systems?
Early computing used binary prefixes (e.g., ) for memory alignment. However, the SI system () was already established for metric units. The IEC standardized binary prefixes in 1999 to resolve confusion.