Data Storage Converter — GB, MB, GiB, TB, bits & bytes

How it works

Storage sizes come in two families of prefixes, and mixing them up is the source of endless confusion (NIST):

• Decimal (SI) prefixes step by 1000: 1 kilobyte (KB) = 1000 bytes, 1 megabyte (MB) = 1000 KB, 1 gigabyte (GB) = 1000 MB, 1 terabyte (TB) = 1000 GB. Drive manufacturers, networks and most specifications use these.
• Binary (IEC) prefixes step by 1024 (2¹⁰): 1 kibibyte (KiB) = 1024 bytes, 1 mebibyte (MiB) = 1024 KiB, 1 gibibyte (GiB) = 1024 MiB. Operating systems (notably Windows) often report sizes this way while labelling them "GB".
• And 1 byte = 8 bits, so file and memory sizes are in bytes while network speeds are in bits.

The calculator converts your value to the base unit (the byte) and then to the unit you want, so any pairing — GB↔MB, GiB↔MiB, TB↔GiB — works through that common base. Because the two families differ, 1 GB (10⁹ bytes) is only about 0.9313 GiB (2³⁰ bytes).

Worked example

Converting 1 gigabyte to megabytes (both decimal):

1 GB = 1000 MB (decimal, ×1000)

But a 1 terabyte drive, measured in binary units, is 10¹² ÷ 2³⁰ ≈ 931.32 GiB — which is why your operating system shows less than the "1 TB" on the box.

Frequently asked questions

How many MB are in a GB?

1000, using decimal (SI) units — the ones drive makers use. In binary units, 1 GiB is 1024 MiB, so it depends on which system you mean.

Why does my hard drive show less space than advertised?

Because drives are sold in decimal units (1 TB = 10¹² bytes) but many operating systems display binary units while still writing "GB". 1 TB is about 931 GiB, so a 1 TB drive shows as roughly 931 GB in those systems.

What is the difference between GB and GiB?

A gigabyte (GB) is 10⁹ bytes (decimal); a gibibyte (GiB) is 2³⁰ = 1,073,741,824 bytes (binary). A GiB is about 7.4% larger than a GB.

How many bits are in a byte?

Eight. Storage is measured in bytes, but data-transfer rates are usually in bits per second, so a 100 megabit connection transfers about 12.5 megabytes per second.

Which system should I use?

Use decimal (GB, TB) for drive capacity and data plans, and binary (GiB, MiB) when matching what an operating system reports. This converter includes both so you can translate between them.

How many kilobytes are in a megabyte?

1000 in decimal units (1 MB = 1000 KB), or 1024 in binary units (1 MiB = 1024 KiB). The names KB and MB usually mean the decimal versions.