A Quantity represents a value associated with a specific unit:

Use to enter quantities and units:

Compound unit expressions can also be found using :

A unit can be a string or a product of strings:

Valid unit specifications include a number of physical constants:

Quantity will automatically attempt to interpret an unknown unit string:

Quantity expressions can be used in comparison functions:

Use MixedMagnitude and MixedUnit specifications to define a mixed Quantity:

Quantity expressions can be used in various list operations:

Many numerical functions also operate on Quantity expressions:

Integer functions also operate on Quantity expressions:

Normal will return the fundamental value for dimensionless Quantity expressions:

N may be used to numericize Quantity expressions:

N will not change the units associated with a Quantity expression, including physical constants:

UnitConvert can be used to find the SI value of physical constants:

Use FormulaData with Quantity objects to determine the escape velocity of the Earth and of the Sun:

Use FormulaData with Quantity objects to visualize the spectral radiance of a black body at temperature 5000 kelvins as a function of wavelength:

A unit can be given as a string or product of strings:

IndependentUnit specifications can also be used:

Units accept prefixes that are used to form decimal multiples and submultiples of units:

In its one-argument form, Quantity automatically sets the magnitude to 1:

The first argument of Quantity can also be a Quantity object, in which case units are multiplied:

Additions of Quantity objects with compatible units will heuristically determine the result units:

Products of Quantity objects with compatible units will heuristically determine the result units:

Subtraction of temperatures in non-absolute scales like Celsius or Fahrenheit produces temperature differences:

Addition of a temperature and a temperature difference gives another temperature:

Operations involving products and divisions of temperatures may convert automatically to kelvins:

This result is equivalent to converting the temperature in advance:

Quantity threads its unit specification over lists:

Canonical unit strings are always plural. Unit descriptions will accurately reflect the singular form of a unit:

Since Quantity is HoldRest, it can accept multiple unit strings of the same dimension:

When quantities are multiplied, the resulting unit is not automatically simplified:

Use UnitSimplify to get a simpler form of the unit:

Use UnitConvert to normalize mixed Quantity expressions to non-mixed Quantity expressions:

Use QuantityArray to describe rectangular arrays of Quantity objects of common units:

Normal converts the structured array into an equivalent normal array of Quantity objects:

Quantity automatically attempts to interpret unrecognized unit strings as canonical units:

Expressions composed of unrecognized unit strings cannot be interpreted in this way:

Instead, the unit should be specified as a single string:

Some units contain Interval expressions, which can result in comparisons returning unevaluated: