The Decimal vs Binary Mismatch

This hard drive capacity calculator converts the manufacturer's decimal gigabyte (10⁹ bytes) into the binary gibibyte (2³⁰ bytes) your operating system reports. Multiply the advertised size by 1000/1024 ≈ 0.9313 to find the OS-visible capacity.

The Math Behind the 6.87%

A 1 TB drive holds exactly 10¹² bytes. But the OS divides by 2³⁰ (1,073,741,824), giving 931.32 GiB — a loss of 68.7 GB, or 6.87% of the label. The gap grows with capacity: a 4 TB drive "loses" about 275 GB.

Not Just a Marketing Trick

Both conventions are legitimate — SI prefixes are decimal, while computer memory is naturally binary. The confusion is a documentation failure, not fraud: the exact byte count is on the drive's spec sheet. Partition tables, filesystems, and reserved space add further visible overhead.