Transmission Rate

Transmission rate is the number of bits sent from one device to another each second. You calculate it by dividing the total number of bits by the time taken in seconds.

Getting the units right

File sizes are usually given in bytes, so multiply by 8 to change them into bits. If the time is in minutes, multiply by 60 to change it into seconds. Keep the calculation in one expression so the order is clear:

transmission rate in bits per second = (file size in bytes × 8) ÷ time in seconds

Binary storage prefixes (kibi-, mebi-, gibi- and tebi-) use powers of 1024, so a mebibyte is 1024^2 bytes. Bit-rate prefixes such as mega- are decimal: one megabit is 1000^2 bits. To give the answer in megabits per second, divide the bits per second by 1000^2.

Worked example

A 4 mebibyte game save file is uploaded to cloud storage in 20 seconds. In bits, the file is 4 × 1024^2 × 8 = 33,554,432 bits. Dividing by 20 seconds gives 1,677,721.6 bits per second. Dividing by 1000^2 gives about 1.68 megabits per second.

As one expression:

(4 × 1024^2 × 8) ÷ (20 × 1000^2) = 1.6777216 Mbps