About

Misidentifying data units costs real money. Cloud providers bill in GiB (gibibytes, 2³⁰ bytes) while hard drive manufacturers label in GB (gigabytes, 10⁹ bytes). That 8.7% discrepancy compounds across petabyte-scale infrastructure. This calculator converts any value across 13 data-size units - covering both IEC binary prefixes (KiB, MiB, GiB, TiB, PiB, EiB) and SI decimal prefixes (KB, MB, GB, TB, PB, EB) - plus raw bits and bytes. Every factor is exact: binary units use powers of 2, decimal units use powers of 10. No rounding errors propagate.

Limitation: this tool operates on static conversion factors. It does not account for filesystem overhead, block alignment, or RAID parity. A 1TB drive formatted with NTFS yields roughly 931GiB usable space, not because of a conversion error, but because manufacturers use decimal gigabytes while operating systems report binary gibibytes. Use this calculator to verify vendor claims and budget storage procurement accurately.

Formulas

The conversion from any source unit to any target unit passes through bytes as the canonical intermediate representation:

V_target = V_source × F_sourceF_target

Where V_source is the input value, F_source is the number of bytes in one source unit, and F_target is the number of bytes in one target unit. For binary (IEC) prefixes, the factor follows 2ⁿ progression:

F_binary = 2^{(10 × k)}

Where k = 1 for KiB, 2 for MiB, 3 for GiB, 4 for TiB, 5 for PiB, 6 for EiB. For decimal (SI) prefixes:

F_decimal = 10^{(3 × k)}

Where k = 1 for KB, 2 for MB, 3 for GB, 4 for TB, 5 for PB, 6 for EB. Bits use F = 0.125 (one-eighth of a byte).

Reference Data

Unit	Symbol	Standard	Bytes Equivalent	Factor
Bit	b	Basic	0.125	1/8 byte
Byte	B	Basic	1	8 bits
Kilobyte	KB	SI (Decimal)	1,000	10³
Kibibyte	KiB	IEC (Binary)	1,024	2¹⁰
Megabyte	MB	SI (Decimal)	1,000,000	10⁶
Mebibyte	MiB	IEC (Binary)	1,048,576	2²⁰
Gigabyte	GB	SI (Decimal)	1,000,000,000	10⁹
Gibibyte	GiB	IEC (Binary)	1,073,741,824	2³⁰
Terabyte	TB	SI (Decimal)	1,000,000,000,000	10¹²
Tebibyte	TiB	IEC (Binary)	1,099,511,627,776	2⁴⁰
Petabyte	PB	SI (Decimal)	1,000,000,000,000,000	10¹⁵
Pebibyte	PiB	IEC (Binary)	1,125,899,906,842,624	2⁵⁰
Exabyte	EB	SI (Decimal)	1,000,000,000,000,000,000	10¹⁸
Exbibyte	EiB	IEC (Binary)	1,152,921,504,606,846,976	2⁶⁰

Frequently Asked Questions

Hard drive manufacturers define 1 TB as 10¹² bytes (1,000,000,000,000 bytes). Operating systems like Windows report storage in GiB (gibibytes), where 1 GiB = 2³⁰ = 1,073,741,824 bytes. Dividing 1,000,000,000,000 by 1,073,741,824 yields approximately 931.32 GiB. The discrepancy is purely a labeling difference between SI decimal and IEC binary prefixes, not missing storage.

MB (megabyte) is an SI decimal unit equal to 10⁶ = 1,000,000 bytes. MiB (mebibyte) is an IEC binary unit equal to 2²⁰ = 1,048,576 bytes. The difference is 4.86%. The IEC introduced binary prefixes (kibi-, mebi-, gibi-) in 1998 via IEC 80000-13 to eliminate this ambiguity. In practice, RAM is measured in MiB/GiB (binary), while network speeds and storage marketing use MB/GB (decimal).

1 byte = 8 bits. Network speeds are quoted in bits per second (Mbps), while file sizes are in bytes (MB). A 100 Mbps connection transfers at most 12.5 MB/s (100 ÷ 8). This 8x factor is the most common source of confusion when estimating download times. Additionally, protocol overhead (TCP/IP headers) reduces effective throughput by roughly 3-5%.

At petabyte scale, the gap is substantial. 1 PB (SI) = 1,000,000,000,000,000 bytes, while 1 PiB (IEC) = 1,125,899,906,842,624 bytes - a 12.6% difference. If a cloud provider bills per GiB and you estimate costs using GB, you will underestimate your bill by approximately 7.4% at the terabyte level. For a 10 PB deployment at $0.023/GiB/month, this misestimation costs roughly $1,700/month.

Most discrepancies arise from tools conflating SI and IEC units. A tool labeling "KB" but using 1,024 bytes (the IEC definition of KiB) will disagree with a tool that correctly uses 1,000 bytes for KB. Always verify which standard a tool follows. This calculator explicitly separates binary (KiB, MiB, GiB) from decimal (KB, MB, GB) to prevent such errors.

This calculator supports up to exabytes (EB) and exbibytes (EiB). Values beyond this (zettabytes, yottabytes) exceed JavaScript's safe integer range (2⁵³ − 1 ≈ 9 × 10¹⁵). For exabyte-scale conversions, the calculator uses floating-point arithmetic which maintains approximately 15-16 significant digits of precision. For most practical infrastructure planning, this precision is sufficient.