Measured in binary, a 1 terabyte hard drive has 1,048,576 megabytes of storage space. Hard drive storage space is calculated in bits, and 8 bits of data are in 1 byte; 1,024 bytes equals 1 kilobyte, and 1 terabyte equals 1,099,511,627,776 bytes.
Although operating systems read the amount of space in a hard drive using the binary method, computer storage manufacturers generally market their hard drives' unformatted capacity in decimal mathematics. Using this method to calculate capacity, an unformatted 1-terabyte hard drive can store 1,000,000 megabytes of data. The International Electrotechnical Commission has introduced the new binary prefixes "mebi," "gibi" and "tebi" to resolve the discrepancy, although they are seldom used.