File Size Converter
File sizes are expressed in two different systems that use the same-sounding names but different numbers, and this causes persistent confusion when you compare what a hard drive manufacturer says versus what your operating system reports. The decimal SI system, used by drive makers and most consumer products, defines a kilobyte as 1,000 bytes, a megabyte as 1,000,000 bytes and a gigabyte as 1,000,000,000 bytes. The binary IEC system, technically more correct for computer memory and historically used by operating systems, defines a kibibyte (KiB) as 1,024 bytes, a mebibyte (MiB) as 1,048,576 bytes and a gibibyte (GiB) as 1,073,741,824 bytes. The gap between them grows at each step: 1 GiB is about 7 percent larger than 1 GB, which is why a 1 TB drive shows up as roughly 931 GiB in Windows. This converter takes a file size in any unit and displays all the common equivalents in both systems, including megabits (Mb) for bandwidth calculations since internet speeds are measured in megabits per second. Enter a value, choose the unit, and all conversions update instantly. The worked example below uses 1.5 GB as the default input.
Decimal: 1 KB = 1,000 bytes. Binary IEC: 1 KiB = 1,024 bytes. Megabits = Megabytes x 8.
How it works
The input value is converted to bytes first using the appropriate multiplier: decimal units use powers of 1,000 and binary IEC units use powers of 1,024. From the byte count, all other values are derived by dividing by the relevant multiplier. Megabits are bytes multiplied by 8 divided by 1,000,000. The same byte total is divided by 1,024 for KiB, 1,048,576 for MiB and 1,073,741,824 for GiB.
Worked example
Starting with 1.5 GB (decimal): 1.5 times 1,000,000,000 equals 1,500,000,000 bytes. In MB that is 1,500 MB. In megabits that is 12,000 Mb. In binary IEC, 1,500,000,000 divided by 1,048,576 equals approximately 1,430.51 MiB, and divided by 1,073,741,824 equals approximately 1.40 GiB. These match the defaults pre-filled above.
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