# Units of measurement in DU Meter

DU Meter follows certain conventions for reporting data amount and data transfer rate. Although several
standards exist for prefixes and abbreviations used in telecommunications industry, these standards are
largely ignored and abbreviations are often used incorrectly, which leads to misunderstanding and confusion.
This page documents conventions and abbreviations used in DU Meter.

DU Meter has a configuration option that affects reporting. When "Follow IEC 60027-2 (KiB, MiB)" option is
enabled, DU Meter strictly follows SI and IEC 60027-2 standards. Since most users are not accustomed to these
abbreviations, this mode is disabled by default.

### Data amount

DU Meter reports data transfer totals in bytes. Each byte consists of 8 bits, which is basic unit of
information. The following table documents abbreviations and multipliers used in DU Meter:

| Multiplier | Normal mode | IEC 60027-2 |
|---|---|---|
| 1024 | KB | KiB |
| 1024*1024 | MB | MiB |
| 1024*1024*1024 | GB | GiB |
| 1024*1024*1024*1024 | TB | TiB |
| 1024*1024*1024*1024*1024 | PB | PiB |

### Data transfer rate units

Data transfer speeds (bitrates) are most often quoted in 'bits per second', or multiples of that unit. This is
a standard practice in the telecommunications industry. However, some users prefer 'bytes per second', which
are sometimes more handy, since file sizes are always reported in bytes and not bits. DU Meter uses 'bits per
second' units by default, but the alternative 'bytes per second' mode can be chosen in DU Meter options if
preferred.

Even though data amount multipliers are binary (1024 bytes in one kilobyte), data transfer rate multipliers
are decimal when bits are used (1000 bits per second is one kilobit per second) and binary when bytes are used
(1024 bytes per second is one kilobyte per second). This notion is confusing, but universally accepted,
therefore DU Meter follows it.

Data transfer rate abbreviations in bits per second mode:

| Multiplier | Normal mode | SI |
|---|---|---|
| 1 | bps | bit/s |
| 1000 | kbps | kbit/s |
| 1000*1000 | Mbps | Mbit/s |
| 1000*1000*1000 | Gbps | Gbit/s |
| 1000*1000*1000*1000 | Tbps | Tbit/s |
| 1000*1000*1000*1000*1000 | Pbps | Pbit/s |

Data transfer rate abbreviations in bytes per second mode:

| Multiplier | Normal mode | IEC 60027-2 |
|---|---|---|
| 1 | B/s | B/s |
| 1024 | KB/s | KiB/s |
| 1024*1024 | MB/s | MiB/s |
| 1024*1024*1024 | GB/s | GiB/s |
| 1024*1024*1024*1024 | TB/s | TiB/s |
| 1024*1024*1024*1024*1024 | PB/s | PiB/s |

### Reference

1. [Prefixes for binary multiples (NIST Reference)](https://physics.nist.gov/cuu/Units/binary.html)
1. ["byte" in Wikipedia](https://en.wikipedia.org/wiki/Byte)
1. ["bitrate" in Wikipedia](https://en.wikipedia.org/wiki/Bitrate)