How many bits are in a byte?

Eight. That has been the universal standard since the 1960s, and networking documents call an eight-bit byte an octet.

What is half a byte called?

A nibble: four bits, enough for one hexadecimal digit from 0 to F.

How many bytes per second is 320 kbps?

40,000 bytes per second, or 40 KB/s. Divide the bit rate by 8.

How many bytes is a 2048-bit RSA key?

256 bytes for the key's modulus. The full key file is larger because it stores extra fields and encoding.

Bits to Bytes

One byte is eight bits, so divide a number of bits by 8 to get bytes: 64 bits are 8 bytes and 1,000 bits are 125 bytes. The same rule turns any bitrate, such as kbps or Mbps, into bytes per second.

Bits to bytes at a glance

Seven values you meet most often. The tables and the converter handle everything in between.

1 bit
0.125 B
2 bit
0.25 B
5 bit
0.625 B
10 bit
1.25 B
20 bit
2.5 B
50 bit
6.25 B
100 bit
12.5 B

Why a byte is eight bits

A bit is a single binary digit, 0 or 1. Early computers grouped bits into characters of six, seven or nine bits; the word byte was coined at IBM in 1956, and the IBM System/360 of 1964 made the eight-bit byte the norm. Eight bits give 256 values, enough for letters, digits and symbols with room to spare, and every mainstream processor since has used it. Networking standards call it an octet to remove any doubt.

Text shows the link clearly: plain ASCII letters fit in one byte, while UTF-8 uses one to four bytes per character, so an emoji usually needs 32 bits. A 256-bit encryption key is 32 bytes, an IPv4 address is 32 bits or 4 bytes, and an IPv6 address is 128 bits or 16 bytes.

How to convert bits to bytes

Start with the value in bits.
Divide it by 8, which is the same as multiplying by 0.125.
Round the result to the precision the job needs: whole numbers for everyday use, more decimals for engineering or recipes.

From bitrate to file size

Media is described in bits per second, files in bytes, so the factor of eight sits between them. An MP3 at 320 kbps uses 40 KB each second, about 2.4 MB per minute. A 1080p video at 8 Mbps uses 1 MB each second, 60 MB per minute and 3.6 GB per hour.

Turn it around to hit a size limit: to fit a 60-second clip into 10 MB you have 80 megabits for the whole minute, so the combined video and audio bitrate must stay under about 1.33 Mbps. That is the calculation compress video to 10 MB does for you.

Bits in images

Color depth is quoted in bits per pixel. Standard 24-bit color stores 3 bytes per pixel, so an uncompressed 1920 × 1080 frame is 6,220,800 bytes, about 6.2 MB; formats such as JPEG and PNG shrink it from there. To find the pixel dimensions for a print or document size, use the pixel converter. For internet speeds specifically, see megabits to MB.

Frequently asked questions

How many bits are in a byte?: Eight. That has been the universal standard since the 1960s, and networking documents call an eight-bit byte an octet.
What is half a byte called?: A nibble: four bits, enough for one hexadecimal digit from 0 to F.
How many bytes per second is 320 kbps?: 40,000 bytes per second, or 40 KB/s. Divide the bit rate by 8.
How many bytes is a 2048-bit RSA key?: 256 bytes for the key's modulus. The full key file is larger because it stores extra fields and encoding.