How Many GB in a Terabyte?
There are two answers, and both are right: 1000 if you ask the company that sold you the drive, and 1024 if you ask the computer you plug it into. That single disagreement is the reason your brand-new "1 TB" drive shows up as 931 GB.
The missing gigabytes aren't missing
Storage is sold in decimal: a manufacturer's "terabyte" is a clean trillion bytes (1,000,000,000,000). Your operating system, though, thinks in binary, because memory is addressed in powers of two. To turn bytes into "GB" it divides by 1024 three times — and a trillion bytes divided that way comes to about 931, not 1000. So the drive holds every byte promised; Windows is just labelling them in a different counting system. The widget below shows the exact figure for any size you type.
The gap gets worse the bigger the drive
The mismatch compounds at every step up the ladder. A kilobyte is off by about 2.4%, a megabyte by 4.9%, a gigabyte by 7.4% — and a terabyte by very nearly 10%. That's why the problem barely registered in the floppy-disk era and feels glaring now: a "4 TB" drive appears to "lose" the better part of 370 GB. It hasn't, but the percentage is large enough that people notice and assume they've been short-changed.
People actually sued over this
The confusion was costly enough to reach court. In the mid-2000s, drive makers including Western Digital and Seagate faced US class-action suits arguing their capacities were overstated because buyers saw fewer "GB" in their operating system than the box advertised. The cases settled, and the legacy is the small print you still see today — a line on the packaging clarifying that "1 GB = 1,000,000,000 bytes" and that usable capacity will appear lower once formatted. The maths was always sound; the labelling was the problem.
Frequently asked questions
How many GB are in a TB?
It depends which system you mean. The decimal system used to sell storage says 1 TB = 1000 GB. The binary system your computer uses says 1 TiB = 1024 GiB. Both are correct; they're just counting in different bases.
Why does my 1 TB drive show only 931 GB?
The box uses decimal (1 TB = a trillion bytes). Windows divides those same bytes by 1024 three times to get "GB", which yields about 931. No space is lost — it's a labelling mismatch. macOS sidesteps it by using decimal, so a 1 TB drive reads close to 1000 GB there.
How much is half a terabyte in GB?
500 GB in decimal terms (how a 500 GB drive is sold), which your computer will display as roughly 465 GB in its binary count.
Which is correct, 1000 or 1024?
Strictly, 1000 GB = 1 TB and 1024 GiB = 1 TiB — the units are different. The confusion is that almost everyone, including Windows, writes "GB" when they mean GiB. The official binary prefixes (KiB, MiB, GiB, TiB) exist to fix exactly this.
- SI / decimal prefixes: 1 TB = 10¹² bytes = 1000 GB — the convention used by storage manufacturers and networking.
- IEC 80000-13 binary prefixes: 1 TiB = 2⁴⁰ bytes = 1024 GiB — the convention Windows and RAM use while labelling it "GB".
- A 1 TB (10¹² byte) drive displays as ≈ 931 GiB because 10¹² ÷ 2³⁰ ≈ 931.3.
- US class-action settlements against hard-drive makers (Western Digital, Seagate, mid-2000s) over advertised vs displayed capacity.
1000 or 1024 — the honest answer is that your drive holds exactly what it says, in a unit your computer politely refuses to use.