Why does my 1 TB hard drive show as 931 GB?

The drive holds a trillion bytes, which is a terabyte in decimal. Windows divides by 1024 three times, giving 931, but labels the result GB rather than GiB. Both figures describe the same drive.

What is the difference between MB and MiB?

A megabyte is 1,000,000 bytes; a mebibyte is 1,048,576. The binary units — KiB, MiB, GiB — were standardised in 1998 precisely to end this ambiguity, though adoption is still patchy.

How many megabytes are in a gigabyte?

1,000 using decimal prefixes, or 1,024 if you mean mebibytes in a gibibyte. Which one is correct depends entirely on which system the source was using.

What is the difference between a bit and a byte?

A byte is eight bits. Network speeds are quoted in bits per second and file sizes in bytes, so a 100 Mbps connection downloads at about 12.5 MB/s at best — the factor of eight surprises people constantly.

Why do network speeds use bits instead of bytes?

Historical convention from telecommunications, where the bit is the natural unit of a serial line. It also produces a larger number, which providers have never been in a hurry to change.

Data Size Converter

Convert bytes, KB, MB, GB and TB — including the 1024-based binary units.

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About the Data Size Converter

Convert between bytes, kilobytes, megabytes, gigabytes and their binary counterparts in one place. Values update as you type, and the result is calculated by converting to a base unit and back — so the arithmetic is the same in both directions and round-tripping a number returns exactly what you started with.

There are two systems and they are routinely confused. Decimal prefixes count in powers of 1,000 — a kilobyte is 1,000 bytes — and binary prefixes count in powers of 1,024, written KiB, MiB and GiB. The gap compounds: a kilobyte and a kibibyte differ by 2.4 percent, a gigabyte and a gibibyte by 7.4 percent.

This is the whole explanation for the missing space on a new drive. Manufacturers sell in decimal, so a '1 TB' drive holds 1,000,000,000,000 bytes. Windows reports in binary but labels it TB, so it shows 931 GB. Nothing is missing and no one is lying — the same number is being divided by 1024 and labelled as though it were divided by 1000.

How it works

Type a value and choose the units to convert between.
The result updates as you type, with the same value shown in every other unit below.
Jump straight to a direct page for the common conversions listed at the bottom.

Frequently asked questions

Why does my 1 TB hard drive show as 931 GB?: The drive holds a trillion bytes, which is a terabyte in decimal. Windows divides by 1024 three times, giving 931, but labels the result GB rather than GiB. Both figures describe the same drive.
What is the difference between MB and MiB?: A megabyte is 1,000,000 bytes; a mebibyte is 1,048,576. The binary units — KiB, MiB, GiB — were standardised in 1998 precisely to end this ambiguity, though adoption is still patchy.
How many megabytes are in a gigabyte?: 1,000 using decimal prefixes, or 1,024 if you mean mebibytes in a gibibyte. Which one is correct depends entirely on which system the source was using.
What is the difference between a bit and a byte?: A byte is eight bits. Network speeds are quoted in bits per second and file sizes in bytes, so a 100 Mbps connection downloads at about 12.5 MB/s at best — the factor of eight surprises people constantly.
Why do network speeds use bits instead of bytes?: Historical convention from telecommunications, where the bit is the natural unit of a serial line. It also produces a larger number, which providers have never been in a hurry to change.

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