Data storage conversion has a famous trap: there are two different 'kilobytes.' Storage manufacturers and the SI system use decimal units — 1 kilobyte (kB) = 1,000 bytes, 1 megabyte (MB) = 1,000,000 bytes, 1 gigabyte (GB) = 1,000,000,000 bytes. Operating systems and memory engineers traditionally use binary units — 1 kibibyte (KiB) = 1,024 bytes, 1 mebibyte (MiB) = 1,048,576 bytes, 1 gibibyte (GiB) = 1,073,741,824 bytes. The two systems agree at small sizes and diverge as they grow: by the terabyte, the gap is about 10 percent. This is exactly why a '1 TB' hard drive shows up as roughly 931 GB in your operating system — the drive holds 10^12 bytes, and the OS divides by 2^30.
The full ladder, decimal: bit, byte (8 bits), kB (10^3), MB (10^6), GB (10^9), TB (10^12), PB (10^15). Binary equivalents use KiB, MiB, GiB, TiB, PiB with powers of 1,024. Network speeds add a second trap: they are quoted in bits per second (Mbps), while file sizes are in bytes — so a '100 Mbps' connection downloads at a theoretical maximum of 12.5 megabytes per second, and real-world overhead takes another 10 percent or so off that.
For practical conversions, decide which system your context uses: hard drives, SSDs, and USB sticks are sold in decimal units; RAM and operating-system displays use binary; internet plans use bits. Convert within one system by powers of 1,000 or 1,024, and cross between bits and bytes by factors of 8. This calculator handles both systems and the bit/byte divide explicitly.