Digital Storage Converter
Digital storage capacity is measured in bytes and their multiples, but a critical distinction exists between SI (decimal) and IEC (binary) units that often confuses consumers and professionals alike. The SI prefixes (kilobyte, megabyte, gigabyte, terabyte, petabyte) use powers of 1,000, following the standard metric system. The IEC prefixes (kibibyte, mebibyte, gibibyte, tebibyte) use powers of 1,024, reflecting how computer memory and storage actually work in binary systems. This distinction became obvious when buyers noticed that a 1 TB hard drive, calculated as 1 trillion bytes using SI units, appears as only 931 GiB on a computer using IEC binary units. Storage manufacturers market using SI units (simpler, larger numbers), while operating systems historically displayed storage using binary units but incorrectly labelled them with SI prefixes, creating decades of confusion. The bit remains the smallest unit: 8 bits equal 1 byte, and bits are used for data transfer rates (such as Mbps for megabits per second), while bytes measure storage. Understanding both standards is essential when comparing cloud storage, evaluating device specifications, or calculating actual storage available for files. This calculator displays eleven storage units: bits, bytes, and SI units up to petabytes, plus IEC binary units up to tebibytes. Enter a value in any field and all others update instantly.
NIST conversion factors
All conversions below use exact factors: SI prefixes use powers of 1,000 (decimal), IEC prefixes use powers of 1,024 (binary). All units are expressed relative to the byte.
| Unit | Symbol | Bytes |
|---|---|---|
| Bit | bit | 0.125 |
| Byte | B | 1 |
| Kilobyte (SI) | KB | 1,000 |
| Megabyte (SI) | MB | 1,000,000 |
| Gigabyte (SI) | GB | 1,000,000,000 |
| Terabyte (SI) | TB | 1,000,000,000,000 |
| Petabyte (SI) | PB | 1,000,000,000,000,000 |
| Kibibyte (IEC) | KiB | 1,024 |
| Mebibyte (IEC) | MiB | 1,048,576 |
| Gibibyte (IEC) | GiB | 1,073,741,824 |
| Tebibyte (IEC) | TiB | 1,099,511,627,776 |
Digital storage converter: frequently asked questions
What is the difference between SI and IEC prefixes?
SI prefixes (kilo, mega, giga, tera) use powers of 1,000 (decimal). IEC prefixes (kibi, mebi, gibi, tebi) use powers of 1,024 (binary). Storage manufacturers use SI (decimal) for marketing, while operating systems traditionally showed binary values using SI labels, causing confusion. This calculator distinguishes both.
Why does my hard drive seem smaller than advertised?
A 1 TB hard drive has 1 trillion bytes (SI definition), which equals approximately 931 GiB (binary definition). Operating systems traditionally displayed storage using binary units with SI labels, making a 1 TB drive appear as about 931 GB. Modern systems clarify the distinction.
What is a bit?
A bit is the smallest unit of digital information, representing a single binary digit (0 or 1). Eight bits equal one byte. Bits are used in telecommunications and data transfer rates (megabits per second or Mbps), while bytes are used for storage capacity.
How precise are these conversions?
These conversions use exact powers of 1,000 (SI) and 1,024 (IEC). One byte equals exactly 8 bits, 1 kilobyte (SI) equals exactly 1,000 bytes, and 1 kibibyte (IEC) equals exactly 1,024 bytes.
When should I use which standard?
Use SI units (KB, MB, GB, TB) for marketing and general storage capacity. Use IEC units (KiB, MiB, GiB, TiB) for precise technical specifications and when calculating actual computer memory and storage access. Cloud providers typically use SI units.
Official sources
- NIST Special Publication 330: The International System of Units.
- IEC 80000-13: International Electrotechnical Commission standard for binary prefixes.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.