Units and symbols
Use consistent formatting, terminology, and symbols to display units of measure in your UI. Units of measure and symbols often appear when describing quantitative values including:
- Date and time.
- Data storage.
- Data bandwidth.
When providing quantitative values in your UI, use the International System of Units (SI units) so that your units of measure can be understood by global users. Use the following base units and symbols to describe different quantities:
- Length: meter (m)
- Mass: kilogram (kg)
- Electric current: ampere (A)
- Thermodynamic temperature: kelvin (K)
- Amount of substance: mole (mol)
- Luminous intensity: candela (cd)
Whenever possible, write the full name of each time unit.
Example: Write "6 minutes" instead of "6 min."
If space is limited, use symbols to communicate the same units of time in less space:
- Millisecond (ms)
- Second (s)
- Minute (min)
- Hour (hr)
Avoid using symbols for days, weeks, months, and years.
Computer storage and memory are typically measured in bytes. Bytes can be shown in binary units (gibibytes) or decimal/metric units (gigabytes).
Use binary units to express amounts of digital information in alignment with most computing and open source software. This consistency eliminates confusion.
Bandwidth is the amount of data transferred from one point to another within a network in a specified amount of time.
Data transfer is primarily measured in two ways:
- Megabits/second (Mbps): Specifies download and upload speeds on the internet
- Megabytes/second (MBps): Specifies the quantity of data or file size transferred over time
Data transfer rates can be measured in binary or metric units. Always align this unit with the scale you use to measure data size.
Note: Pay special attention to letter case when writing symbols for bits (b) and bytes (B). Eight bits (b) make up one byte (B), so using the wrong symbol will change your meaning.
Writing units of measure
Follow these general best practices for writing units of measure:
|Use consistent units, and avoid mixing them.||Write 10 to 75 seconds instead of 10 seconds to 1.25 minutes.|
|Include a space between numbers and units, except for percentages.||Add a space to 75 kg but not to 75%.|
|Display the full name of each unit unless space is limited.||Write 6 seconds ago instead of 6s ago.|
|Don't make unit symbols plural.||Write 60 cm, not 60 cms.|
|Don't punctuate unit symbols unless they end a sentence.||60 cm doesn't end this sentence, so "cm" isn't followed by a period.|
|Write SI unit symbols in lowercase, unless a symbol is named after a person or proper noun, then capitalize its first letter.||Write W for watt. |
Write Hz for hertz.
|Don't mix symbols or apply mathematical operations to unit names.||Write kg/m3 instead of kilogram/m3. |
Write kg · m-3 instead of kilogram/cubic meter.
Use kilogram per cubic meter instead of kg/cubic meter, kilogram per meter3, or kg per m3.
|Use parentheses to display a secondary unit of measure.||10°C (50°F)|
|Clearly express units for two or more related quantities. If necessary, you can include the unit after each numeral.||Write 6 to 8 inches or 6 inches to 8 inches.|
|Use symbols to display derived units of measure (units formed using a calculation).||38 mph, 27 ft/s2|
|For derived units of measure, use the symbol that represents its word form, since it will be more familiar to your users.||Use Hz for Hertz instead of the derivation cycles per second (cycles/second).|
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