Data storage converter

Both families are listed separately: kilobytes, megabytes and gigabytes counting in thousands, and kibibytes, mebibytes and gibibytes counting in 1,024s. Mixing them is why a 1 TB drive shows up as 931 GB.

The discrepancy is not a swindle, but it is a genuine ambiguity. Drive manufacturers use the SI meaning, where a terabyte is 10¹² bytes; Windows displays the same drive using 1,024-based arithmetic while still labelling it "GB", so 10¹² bytes reads as 931. Both numbers describe the same drive. The IEC introduced kibi, mebi and gibi in 1998 specifically to end this, and macOS and Linux now report in the SI sense — Windows is the main holdout. The other thing worth watching is bits versus bytes: network speeds are in bits per second, so a 100 Mbps connection downloads at about 12.5 MB/s at best.