What is a terabyte (TB)?
A terabyte (TB) is a unit of digital information storage used in computing. It is commonly understood in two contexts:
- SI (International System of Units) Definition:
- 1 TB=1012 bytes=1,000,000,000,000 bytes
- Used by storage manufacturers (e.g., hard drives, SSDs).
- Binary (IEC) Definition:
- 1 tebibyte (TiB)=240 bytes=1,099,511,627,776 bytes
- Used in software and operating systems for memory addressing.
The distinction prevents confusion between decimal (base-10) and binary (base-2) systems.
Understanding data measurement systems
SI system (base-10)
The SI system follows powers of 10, ideal for simplifying large numbers in commerce and engineering:
- 1 kilobyte (KB)=103 bytes
- 1 megabyte (MB)=106 bytes
- 1 gigabyte (GB)=109 bytes
- 1 terabyte (TB)=1012 bytes
Binary system (IEC standard, base-2)
Computers use binary, so the IEC standardized units for clarity:
- 1 kibibyte (KiB)=210 bytes=1,024 bytes
- 1 mebibyte (MiB)=220 bytes
- 1 gibibyte (GiB)=230 bytes
- 1 tebibyte (TiB)=240 bytes
To convert terabytes (TB or TiB) to bits:
For SI (TB to bits):
Bits=TB×(1012)×8
For IEC (TiB to bits):
Bits=TiB×(240)×8
Explanation:
- Multiply terabytes by 1012 (SI) or 240 (IEC) to get bytes.
- Convert bytes to bits by multiplying by 8 (since 1 byte = 8 bits).
Examples
Example 1: Converting 2 TB to Bits (SI)
2 TB=2×1012×8=1.6×1013 bits
Practical use: A 2 TB hard drive stores 1.6×1013 bits.
Example 2: Converting 1 TiB to Bits (IEC)
1 TiB=1×240×8=8,796,093,022,208 bits
Practical use: Operating systems report 1 TiB as approximately 8.8 trillion bits.
Example 3: Comparing TB and TiB
A 1 TB SSD (SI) offers 1×1012×8=8×1012 bits.
A 1 TiB SSD (IEC) offers 8,796,093,022,208 bits.
Difference: 8.796×1012−8×1012=796 billion extra bits in TiB.
Notes
- Unit symbols: Use uppercase “B” for bytes and lowercase “b” for bits (e.g., 1 MB = 1 megabyte, 1 Mb = 1 megabit).
- Storage vs. transmission: Internet speeds are measured in bits per second (bps), while storage uses bytes.
- Historical context: The IEC introduced binary prefixes (e.g., “tebibyte”) in 1998 to resolve ambiguity between decimal and binary units.
- File size comparison: Compare GB, TB, and PB in real-world contexts (e.g., 1 TB ≈ 250,000 photos).
- Binary-decimal confusion: Why a 1 TB drive shows as ~931 GB in Windows (due to TiB vs. TB).
Frequently Asked Questions
How many bits are in a TB?
Using the SI system:
1 TB=1012 bytes×8=8×1012 bits
This equals 8,000,000,000,000 bits.
Why do storage devices show less capacity than advertised?
A 1 TB drive marketed using SI units (1012 bytes) is displayed as ~931 GiB in Windows, which uses IEC units:
2301012≈931.32 GiB
How to convert 5 TiB to bits?
Using the IEC formula:
5 TiB=5×240×8=43,980,465,111,040 bits
What is the difference between TB and TiB?
- 1 TB=1012 bytes (SI).
- 1 TiB=240 bytes (IEC).
The TiB is ~9.95% larger than the TB.
How are bits used in internet speeds?
If your internet speed is 100 Mbps (megabits per second), downloading 1 TB (SI) of data would take:
100×106 bps8×1012 bits=80,000 seconds≈22.2 hours