Bits & Bytes Explainer
AvailableBits versus bytes, decimal versus binary prefixes, and how storage units and network speeds relate — with exact comparison tables and an interactive converter.
Bits and bytes in one minute
8 bits = 1 byte (here the byte 10110010 = 178)
- A bit (b) is one binary digit: 0 or 1. A byte (B) is 8 bits and can hold 256 different values.
- Storage and files are measured in bytes: 5 MB photo, 1 TB drive.
- Network speeds are measured in bits per second: 100 Mbit/s plan, 1 Gbit/s Ethernet. Divide by 8 for bytes per second.
- Watch the case: Mb is megabit, MB is megabyte — a factor of 8.
Try it
Decimal (SI) vs binary (IEC) prefixes
SI prefixes are powers of 1000; IEC prefixes are powers of 1024. The gap grows with each step.
| SI prefix | Bytes | IEC prefix | Bytes | IEC larger by |
|---|---|---|---|---|
| kilo (kB) | 1,000 | kibi (KiB) | 1,024 | 2.4% |
| mega (MB) | 1,000,000 | mebi (MiB) | 1,048,576 | 4.86% |
| giga (GB) | 1,000,000,000 | gibi (GiB) | 1,073,741,824 | 7.37% |
| tera (TB) | 1,000,000,000,000 | tebi (TiB) | 1,099,511,627,776 | 9.95% |
| peta (PB) | 1,000,000,000,000,000 | pebi (PiB) | 1,125,899,906,842,624 | 12.59% |
Network speeds in bytes per second
Maximum values at 100% of the line rate. Real throughput is lower because of protocol overhead and other traffic.
How long do typical downloads take?
Illustrative file sizes; theoretical time at full speed.
Calculate your own: Bandwidth Calculator (download and transfer times) · Data Storage Converter · Unit Converter
How it works
A bit is a single binary digit (0 or 1); a byte is 8 bits. Storage is measured in bytes, network speeds in bits per second. Prefixes come in two families: decimal (SI: k, M, G = powers of 1000) and binary (IEC: Ki, Mi, Gi = powers of 1024). The tables on this page are calculated exactly from these definitions.
Frequently asked questions
Why are bits written “b” and bytes “B”?
By convention lowercase b means bit and uppercase B means byte, so Mb is megabit and MB is megabyte. Writing Mbit and MB avoids confusion.
Where did binary prefixes come from?
Computer memory comes in powers of two, so “kilo” was long used loosely for 1024. In 1998 the IEC introduced kibi (Ki), mebi (Mi), gibi (Gi) and so on to separate the two meanings.
Is 1 Gbit/s Ethernet 1 GB per second?
No: 1 Gbit/s is at most 125 MB/s (1,000,000,000 ÷ 8 bytes per second), and a little less after protocol overhead.