Bits to bytes converter

Examples: where bit counts need to become bytes

• Keys and hashes. Security settings are described by bit length. A 128-bit value is 16 bytes and a 256-bit value is 32 bytes, which is what you allocate in a database column or buffer.
• Data volume from a meter. A monitoring tool reports that a device sent 4 Gb in a day. That is 0.5 GB (500 MB) of data, which is what counts against a data allowance.
• Protocol fields. Specifications often describe fields in bits: a 32-bit field is 4 bytes, a 48-bit field 6 bytes.
• A speed turned into a total. A link that carried 8,000,000,000 bits in total moved 1,000,000,000 bytes, which is 1 GB. The same division by 8 works at every prefix: Mb to MB, Gb to GB, Tb to TB.

Pitfall: Mb vs MB

A lower-case b is a bit and an upper-case B is a byte. "500 Mb" is 62.5 MB, not 500 MB, and confusing the two makes a figure eight times too large or too small. When someone writes a file size as Mb, check whether they meant megabits; in everyday speech they usually mean megabytes.

Binary units add a second trap: 8,388,608 bits is exactly 1 MiB (1,048,576 bytes) but 1.048576 MB. Pick the unit your source uses. To convert the other way, see bytes to bits. For speeds, where the same factor of 8 applies per second, use Mbps to bytes per second, and read bits vs bytes for why both units exist.