Why Does a Formatted Drive Have Less Space Than Advertised?

 

Formatted drives can appear to have less space than advertised because of differing byte sizes, hidden partitions, SSD overprovisioning, and pre-installed bloatware.

A gallon of milk is a gallon of milk, but a terabyte of hard drive space may not be what it says on the box! The difference between advertised and reported drive capacities is easy to explain.

The Most Common Reason: Different Counting Methods!

Drive manufacturers use a different way of calculating storage capacity than some operating systems. Specifically, Microsoft Windows (along with many other programs) counts storage space in binary bytes, whereas drive makers use decimal bytes.

The difference between decimal and binary bytes is that decimal bytes are based on the decimal (base-10) system, whereas binary bytes are based on the binary (base-2) system. In the decimal system, the basic unit of measurement for digital data storage is the decimal kilobyte, which is equal to 1,000 bytes. In the binary system, there are 1024 bytes in a binary kilobyte.