Drive manufacturers measure storage capacity in decimal (TB) units rather than binary (TiB) units. This leads to much confusion because real-world applications almost always use binary units. To add to the confusion, the IEEE standardized unit notation is often used incorrectly or interchangeably. No, hard drive manufacturers are not cheating you, they are simply using different units of measurement.
- 1 TiB = 1,099,511,627,776 bytes as measured in binary.
- 1 TB = 1,000,000,000,000 bytes as measured in decimal (about ~0.91 TiB).
The IEEE standard is described here: https://en.wikipedia.org/wiki/Byte