Calculate Hard Drive Size in Bytes

Two different mathematical systems are used to define how much information can be stored on the hard disk drive of your computer: binary or base-2 mathematics and base-10 mathematics.

In the binary or base-2 system used by the operating system, 1 gigabyte (GB) is equal to 1,073,741,824 bytes.
In the base-10 system used by hard disk drive manufacturers, 1 gigabyte (GB) is equal to 1,000,000,000 bytes (rather than the 1,073,741,824 bytes, as listed above).
This discrepancy in reporting drive sizes (base-2 vs. base-10) may lead you to believe that you have a hard disk drive of less than expected capacity if you compare the figure reported by the operating system with the figure reported by your documentation, although the actual hard drive size is identical. Microsoft® Windows® counts the size using base-2 math, therefore if you believe your reported hard drive size is smaller than it should be, refer to the chart below for the corresponding base-10 values.

These two mathematical systems produce 2 different numbers but actually the stored space reported by each of them is the same.
If you have noticed this discrepancy, refer to the table below.

Base10   Base2         Base10  Base2
36GB     34.3GB      160GB   152.6GB
40GB     38.1GB      200GB   190.7GB
73GB     69.6GB      250GB   238.4GB
80GB     76.3GB      300GB   286.1GB
100GB   95.4GB      500GB   476.8GB
120GB  114.4GB     750GB   715.3GB
146GB  139.2GB     1000GB 953.7GB
Table 1: Base-10 vs. Base-2  Drive Size Comparisons