How Many GB in a TB? Data Storage Units Explained

There are two correct answers, and that is the whole source of the confusion. In decimal (SI) units, 1 terabyte = 1,000 gigabytes. In binary (IEC) units, 1 terabyte = 1,024 gibibytes. Storage makers advertise the decimal number, while operating systems usually count in binary — which is why a "1 TB" drive shows up as about 931 GB on your computer.

Why there are two different numbers

Computers work in powers of two, so early on a "kilobyte" came to mean 1,024 bytes (2¹⁰) rather than exactly 1,000. That works, but it clashes with the metric system, where kilo always means 1,000. To fix the ambiguity, standards bodies introduced separate binary names: kibibyte (KiB), mebibyte (MiB), gibibyte (GiB) and tebibyte (TiB) for the powers of 1,024, leaving KB, MB, GB and TB for the powers of 1,000.

In practice, hard-drive and SSD manufacturers use the decimal meaning (1 TB = 1,000,000,000,000 bytes) because it gives a bigger, rounder number. Windows reports the same drive using binary math but still labels it "GB", so 1,000,000,000,000 bytes ÷ 1,024³ ≈ 931 — hence the "missing" space.

The full ladder of units

• •8 bits = 1 byte (B) — one character of text.
• •1 kilobyte (KB) = 1,000 bytes · 1 kibibyte (KiB) = 1,024 bytes.
• •1 megabyte (MB) = 1,000 KB · 1 mebibyte (MiB) = 1,024 KiB.
• •1 gigabyte (GB) = 1,000 MB · 1 gibibyte (GiB) = 1,024 MiB.
• •1 terabyte (TB) = 1,000 GB · 1 tebibyte (TiB) = 1,024 GiB.
• •1 petabyte (PB) = 1,000 TB — the next step up.

Common conversions people search

• •1 TB = 1,000 GB (decimal) or 1,024 GiB (binary).
• •2 TB = 2,000 GB · 500 GB = 0.5 TB.
• •1 GB = 1,000 MB · 1 MB = 1,000 KB.
• •A 4K movie is roughly 15–25 GB; a 1 TB drive holds about 40–60 of them.
• •A byte count like 849,346,560 bytes ÷ 1,000³ ≈ 0.85 GB (or ÷ 1,024³ ≈ 0.79 GiB).

Which one should you use?

For buying, planning and everyday math, decimal (1 TB = 1,000 GB) is simplest and matches how storage is sold. When you want to know why your operating system shows a smaller number, switch to binary (÷ 1,024 per step). Both are shown side by side on our data storage converter so you never have to guess which one a site means.

1. 1Decide whether you want decimal (selling/marketing) or binary (what your OS shows).
2. 2For decimal, multiply or divide by 1,000 for each step up or down the ladder.
3. 3For binary, use 1,024 per step instead.
4. 4For an exact byte count, divide by 1,000³ (GB) or 1,024³ (GiB).