Bit
A bit is a single binary digit: 0 or 1.
1 bit = 0 or 1
Binary Basics
Bit vs Byte
A bit stores one binary value. A byte groups eight bits together.
Byte
A byte is eight bits.
1 byte = 8 bits
Quick Conversions
SI and IEC prefixes are different: 1 kB is 1,000 bytes, while 1 KiB is 1,024 bytes. NIST
| Unit | Bits | Bytes |
|---|---|---|
| 1 Byte | 8 Bit | 1 Byte |
| 1 kB (SI) | 8,000 Bit | 1,000 Byte |
| 1 KiB (IEC) | 8,192 Bit | 1,024 Byte |
| 1 MB (SI) | 8,000,000 Bit | 1,000,000 Byte |
| 1 MiB (IEC) | 8,388,608 Bit | 1,048,576 Byte |
Bit vs Byte: Practical Quick Reference
A bit is one binary digit, 0 or 1. A byte is eight bits. The most important notation rule is capitalization: lowercase b means bit, while uppercase B means byte.
| Notation | Meaning | Typical context |
|---|---|---|
b |
bit | link rates, network speeds, low-level flags |
B |
byte | file sizes, storage, memory |
Kb |
kilobit | thousands of bits |
KB |
kilobyte | thousands of bytes |
Mb |
megabit | millions of bits |
MB |
megabyte | millions of bytes |
Gb |
gigabit | billions of bits |
GB |
gigabyte | billions of bytes |
The same 8-to-1 relationship applies when the same decimal prefix is used on both sides. For example, 1 MB = 8 Mb.
b vs B, KB vs Kb, MB vs Mb, and GB vs Gb
The final letter tells you whether the value is in bits or bytes. That distinction changes the quantity by a factor of eight.
8 Kb = 1 KB8 Mb = 1 MB8 Gb = 1 GB
Decimal units such as KB, MB, and GB are commonly based on powers of 1000. Binary IEC units such as KiB, MiB, and GiB use powers of 1024, so check the label when exact capacity matters.
Mbps vs MB/s
Network transfer rates are normally advertised in bits per second, while file sizes and many application download indicators use bytes.
To convert a matching decimal bit rate to bytes per second, divide by eight:
MB/s = Mbps ÷ 8
So 100 Mbps = 12.5 MB/s theoretical maximum before protocol overhead. Real transfers are usually lower because protocols, Wi-Fi conditions, server limits, and storage performance consume part of the available throughput.
Storage vs Network Speed
Storage sizes normally use bytes: KB, MB, GB, TB. Network transfer rates normally use bits per second: Kbps, Mbps, Gbps.
That is why an 800 MB file and a 100 Mbps connection cannot be compared directly. Convert the file size to bits or the link rate to bytes first. Ignoring overhead, 800 MB × 8 = 6400 Mb, and 6400 Mb ÷ 100 Mb/s = 64 seconds as a theoretical minimum.
When estimating downloads, always compare like units and remember that the calculated result is an upper bound rather than a guaranteed real-world rate.
Bits, Bytes, and the Modern 8-Bit Byte
For the historical reasons behind the eight-bit convention—including early byte sizes, 7-bit ASCII, hardware tradeoffs, compatibility, and the term octet—read the history and engineering explanation.