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How many GB in a TB?

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Drive makers use decimal: 1 TB is one trillion bytes exactly. Operating systems use binary: 1 TB of display capacity is 1,099,511,627,776 bytes. When Windows divides the drive's actual capacity (1,000,000,000,000 bytes) by the binary TB value, it ends up with 0.909 TB, or about 931 GB. Nothing is missing. It is a unit mismatch.

Cloud storage providers are split. Google Drive, Dropbox, and iCloud use decimal (1 TB = 1,000 GB). Backblaze and some enterprise providers use binary. If you have exactly 1 TB of storage and you see 1,024 GB or 1,000 GB used differently on two services, that is usually why.

Quick reference: Terabytes to Gigabytes

Terabytes (TB)Gigabytes (GB)
0.5512
11,024
22,048
44,096
88,192
1616,384
3232,768

Worked examples

  1. Example 1: You just bought a 2 TB external drive. How much usable space will Windows show?

    Calculation: 2 TB × 1,000,000,000,000 = 2,000,000,000,000 bytes. Divided by 1,099,511,627,776 = 1.82 TB, or about 1,862 GB.

    Expect Windows to show ~1.82 TB or ~1,862 GB free, minus any filesystem overhead.

  2. Example 2: A cloud plan gives you 1 TB. You upload 900 GB of photos.

    Calculation: 900 GB ÷ 1,000 = 0.9 TB (decimal) or 900 ÷ 1,024 = 0.879 TB (binary).

    On a decimal provider (Google, Dropbox), you still have 100 GB free. On a binary provider, you have 124 GB free.

  3. Example 3: You are comparing a 4 TB drive at $80 to an 8 TB drive at $130. How much is each per GB?

    Calculation: $80 ÷ 4,000 GB = $0.020/GB. $130 ÷ 8,000 GB = $0.01625/GB.

    The 8 TB drive is 19% cheaper per GB. Drives get cheaper per GB at larger sizes, up to a point.

Frequently asked questions

How many GB is 1 TB?

1 TB equals 1,024 GB in binary (what your OS shows) or 1,000 GB in decimal (what the drive box says).

Why does my 1 TB drive only show 931 GB?

The drive actually holds 1 trillion bytes, which is the advertised 1 TB in decimal. Your OS converts that to binary units where 1 TB = 1,099,511,627,776 bytes, so 1 trillion bytes displays as 931.32 GB. No bytes are missing.

Is 1000 GB a terabyte?

In decimal units, yes. 1,000 GB is exactly 1 TB under the SI prefix definition. Drive manufacturers use this definition. In binary units, 1 TB is 1,024 GB.

How many TB is 500 GB?

500 GB is 0.5 TB in decimal or 0.488 TB in binary. Most software will display it as 0.49 TB.

Is TB bigger than GB?

Yes. 1 TB equals about 1,000 GB (exactly 1,024 GB in binary). TB is three orders of magnitude larger than MB.

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