Units and measurements
Write measurements and units clearly and consistently.
Each measurement consists of a value, which indicates the quantity, and a unit of measure, which indicates the standard that the measurement is compared with.
Units
Only standards for physical quantities such as length, weight, and computer memory are considered units of measure. For example, nouns like "users," and "sessions" aren't units. For a list of common units and their abbreviations, refer to List of common units.
Use abbreviations for common units when you're confident that your reader is familiar with them. If the unit you are using is uncommon, or readers might confuse it for a different unit, then write the name of the unit out in full.
Abbreviate units only as part of a measurement. Don't abbreviate units when you write about them in general.
Use metric units in your content. Avoid imperial units as much as possible. If you must use imperial units, then write the name of the unit out in full.
When you write the name of a unit in full, use the singular form only when the value is one. Use the plural form for all other measurements. For example, write "0.5 meters," "1 meter," and "2 meters."
| Incorrect | Correct |
|---|---|
| Measure volume in l. | Measure volume in liters. |
| 24 megapixels | 24 MP |
| 20 t | 20 tonnes |
| 1 meters per second | 1 meter per second |
| 5 d | 5 days |
Measurements
Use numerals for all physical and technical measurements, even if the number is less than 10. For numbers less than one, add a zero before the decimal point.
For most measurements, use a space between the value and the unit.
exceptions
Measurements of angles, temperatures, and prices have separate rules on spacing between the value and the unit.
If the measurement modifies a noun, use a hyphen between the value and the unit.
| Incorrect | Correct |
|---|---|
| one hundred kg | 100 kg |
| 1TB | 1 TB |
| sixty frames per second | 60 frames per second |
| 3 TB hard drive | 3-TB hard drive |
Angles
For angles expressed in degrees, don't use a space between the value and the degree symbol (°).
For angles expressed in radians, use a space between the value and the unit "radians." Avoid expressing degrees in radians unless it's necessary for your content. For example, use radians when writing about some members of the Mathf class that use angles in radians.
| Incorrect | Correct |
|---|---|
| 60 ° | 60° |
| π° rad | π radians Alternatively, write as an angle in degrees unless your content explicitly discusses angles in radians: 180° |
Temperatures
Use a space between the value and the degree symbol (°). Don't use a space between the degree symbol and the abbreviation for the temperature scale.
Express temperatures in degrees Celsius as much as possible. Only use Fahrenheit in informal content when you are confident that most readers understand this scale.
| Incorrect | Correct |
|---|---|
| 22° C | 22 °C |
Prices
Write prices with the currency symbol before the amount. Don't use a space between the symbol and the amount.
Most of the time, prices are in US dollars. When you need to express prices in other currencies, use the currency symbol for that currency. If the currency uses the $ symbol, then include the currency indicator before the symbol.
| Incorrect | Correct |
|---|---|
| 0.25 USD | $0.25 |
| £ 30 | £30 |
| 75 € | €75 |
| 100 CAD | CAD$100 |
Time (duration)
You can write durations of time measured in milliseconds, seconds, or minutes either as a numeral with an abbreviated unit, or as words. If you need to be precise, use numerals and units.
For durations measured in units larger than minutes, write the unit in words. Write numbers between zero and nine as words, and 10 or greater as numerals.
For information about how to write clock times, refer to Dates and times.
| Incorrect | Correct |
|---|---|
| five mins | 5 mins |
| 5 minutes | five minutes |
| 7 hours | seven hours |
| twelve days | 12 days |
Dimensions
For measurements that represent multiple dimensions, separate each numeral with the multiplication symbol (×) surrounded by spaces.
Don't use an "x" to stand in for the multiplication symbol.
If the dimensions have units, then write the unit once, at the end of the dimension expression.
| Incorrect | Correct |
|---|---|
| 3×7 tile grid | 3 × 7 tile grid |
| 1920 x 1080 pixels | 1920 × 1080 pixels |
| 5 m × 8 m | 5 × 8 m |
Rates
Rates express a ratio of one measurement to another. The word "per" separates the two measurement units that define the rate unit. Rates can also involve quantities that aren't usually considered measurements with units. Examples of rates include "meters per second," "dollars per kilogram," and "clicks per session."
Except for the common rates indicated in the common units table, write rate units out in full. Don't replace the word "per" with a slash.
Data transfer rates, such as internet speeds, are often measured in megabits per second (Mbps). Don't confuse bits with bytes, which are more commonly used to measure data storage.
| Incorrect | Correct |
|---|---|
| requests/day | requests per day |
| km/hour | kilometers per hour |
| Mb/s | Mbps |