Why your “2 TB” drive isn't 2 TB
Plug in a brand-new 2 TB drive and Windows says it's 1.81 TB. Nothing is broken and no space is missing — drive makers count in decimal terabytes while your operating system counts in binary tebibytes and labels them “TB.” The gap is about 9%.
A 2 TB drive holds the full 2,000,000,000,000 bytes advertised — your OS just divides by 1,024 four times instead of 1,000, so it prints 1.82 (Windows rounds the display down to about 1.81).
Advertised vs. reported capacity
| Advertised (TB) | OS shows (TiB) | Apparent loss |
|---|---|---|
| 0.5 TB | 0.45 TiB | 9.1% |
| 1 TB | 0.91 TiB | 9.1% |
| 2 TB | 1.82 TiB | 9.1% |
| 3 TB | 2.73 TiB | 9.1% |
| 4 TB | 3.64 TiB | 9.1% |
| 6 TB | 5.46 TiB | 9.1% |
| 8 TB | 7.28 TiB | 9.1% |
| 10 TB | 9.09 TiB | 9.1% |
| 12 TB | 10.91 TiB | 9.1% |
| 14 TB | 12.73 TiB | 9.1% |
| 16 TB | 14.55 TiB | 9.1% |
| 18 TB | 16.37 TiB | 9.1% |
| 20 TB | 18.19 TiB | 9.1% |
| 24 TB | 21.83 TiB | 9.1% |
Frequently asked questions
Why does my 2 TB drive show as 1.81 TB?
Drive makers advertise capacity in decimal terabytes (1 TB = 1,000,000,000,000 bytes), while Windows reports binary tebibytes (1 TiB = 1,099,511,627,776 bytes) but labels them 'TB'. The bytes are all there; the two systems just count differently, a roughly 9% gap.
Is my drive missing storage or defective?
No. The difference is purely how the capacity is labeled, not lost space. A '2 TB' drive holds the full two trillion bytes advertised.
What is the difference between TB and TiB?
A terabyte (TB) is 1,000 to the fourth power bytes. A tebibyte (TiB) is 1,024 to the fourth power bytes, about 10% larger. Operating systems use TiB but often print the label 'TB', which is where the confusion starts.