Data Storage Converter

Q: How many MB are in a GB?

1,000 MB in decimal units SI , or 1,024 MiB in a GiB in binary units IEC . Both are correct: they are different units, and this tool keeps them in separate groups.

Q: What is the difference between KB, kB and KiB?

kB lowercase k is the SI kilobyte of 1,000 bytes. KiB is the IEC kibibyte of 1,024 bytes. "KB" with a capital K is informal and usually means 1,024 bytes, as in older software and in Windows.

Q: Which unit should I use?

Use decimal units kB, MB, GB, TB for disk capacities, file sizes on macOS and anything commercial; use binary units KiB, MiB, GiB for RAM, and to match what Windows and many programmers' tools display.

Data Storage Converter

Convert bits and bytes between kB, MB, GB, TB and KiB, MiB, GiB, TiB, and see why a 1 TB drive shows only about 931 GB in Windows.

Value

From

–

Formula:

Significant figures

≈ means the result was rounded to the chosen number of significant figures.

SI prefixes (kB, MB, GB, TB) are powers of 1,000 and are used by drive makers and macOS. IEC prefixes (KiB, MiB, GiB, TiB) are powers of 1,024; Windows uses them but labels them KB, MB, GB. 1 byte = 8 bits.

{value} in every unit

Unit	Result

Quick conversion table: {from} to {to}

From	To

Common values

Reference	Value	Result

Unit definitions

Unit

How to use the data storage converter

Type a size in Value, for example 1 or 500.
Choose the starting unit in From and the target unit in To. The lists are split into three groups: bits, SI decimal bytes (kB, MB, GB, TB, PB) and IEC binary bytes (KiB, MiB, GiB, TiB, PiB).
The result updates as you type, with the full line below it (“1 TB ≈ 931.32257 GiB”). Copy puts that line on your clipboard.
The Swap units button (⇄) reverses the conversion, and Significant figures sets the rounding (“≈” marks a rounded value).

The tables below show the size in every unit, grouped the same way, a quick conversion table (1, 2, 4, 8… 1,024), common media (floppy disk, CD, DVD, Blu-ray, a “1 TB” drive) and the exact number of bytes in each unit.

Two kinds of kilobyte

Computers count in powers of two, so for decades a “kilobyte” meant 1,024 bytes (2¹⁰), a “megabyte” 1,048,576 bytes, and so on. But “kilo” means 1,000 everywhere else. To end the ambiguity, the IEC defined separate binary prefixes in 1998:

SI decimal	Bytes	IEC binary	Bytes
kilobyte (kB)	1,000	kibibyte (KiB)	1,024
megabyte (MB)	1,000² = 10⁶	mebibyte (MiB)	1,024² = 1,048,576
gigabyte (GB)	10⁹	gibibyte (GiB)	1,073,741,824
terabyte (TB)	10¹²	tebibyte (TiB)	1,099,511,627,776
petabyte (PB)	10¹⁵	pebibyte (PiB)	2⁵⁰ ≈ 1.126 × 10¹⁵

The gap grows with each step: 2.4 % for kilo, 4.9 % for mega, 7.4 % for giga, 10 % for tera and 12.6 % for peta.

Why a “1 TB” drive shows about 931 GB

Drive and memory card makers use SI prefixes: a 1 TB drive holds 1,000,000,000,000 bytes. Windows divides that number by 1,024³ but still writes “GB”, so it displays 10¹² ÷ 1,073,741,824 ≈ 931 GB, which is really 931 GiB. No space is missing: it is the same number of bytes written with two different units. The formatted file system then takes a little more for its own tables. macOS (since 2009) and many Linux tools use decimal units, so they show the same drive as 1 TB. Memory (RAM) is the reverse: a “16 GB” module actually holds 16 GiB.

Bits and bytes

A byte is 8 bits. Storage is measured in bytes (uppercase B, “o” for octet in French), while network speeds are measured in bits (lowercase b). 1 Gbit = 125 MB, and 1 MB = 8 Mbit. For speeds such as Mbit/s and MB/s, use the data transfer rate converter.

Frequently asked questions

How many MB are in a GB?

1,000 MB in decimal units (SI), or 1,024 MiB in a GiB in binary units (IEC). Both are correct: they are different units, and this tool keeps them in separate groups.

Why does my 500 GB drive show 465 GB?

500 × 10⁹ bytes ÷ 1,073,741,824 ≈ 465.66. Windows shows GiB but labels them GB. Convert 500 gigabyte (GB) to gibibyte (GiB) to check.

What is the difference between KB, kB and KiB?

kB (lowercase k) is the SI kilobyte of 1,000 bytes. KiB is the IEC kibibyte of 1,024 bytes. “KB” with a capital K is informal and usually means 1,024 bytes, as in older software and in Windows.

How many bits are in a byte?

Eight. Divide a size in bits by 8 to get bytes: a 1 Gbit memory chip holds 125 MB.

Which unit should I use?

Use decimal units (kB, MB, GB, TB) for disk capacities, file sizes on macOS and anything commercial; use binary units (KiB, MiB, GiB) for RAM, and to match what Windows and many programmers’ tools display.