24.1.1  Notation of unit objects

A unit object has two parts: a real number and a unit expression (a single unit or a multiplicative combination of units). The two parts are linked by the character _ (“underscore”). For example 2_m for 2 meters. For composite units, parenthesis must be used, e.g. 1_(m*s). See Table 24.1 for a list of the basic units.

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_A	Ampere	_ha	Hectare
_Angstrom	Angstrom	_hp	Horsepower
_Bq	Becquerel	_in	Inch
_Btu	Btu British thermal unit	_inH20	Inches of water at 60° Fahrenheit
_Ci	Curie	_inHg	Inches of mercury at 0° Celsius
_F	Farad	_j	Day
_Fdy	Faraday	_kWh	Kilowatt-hour
_Gal	Gal (0.01 m/s2)	_kg	Kilogram
_Gy	Gray	_kip	Kilopound-force
_H	Henry	_km	Kilometre
_Hz	Hertz	_knot	nautical miles per hour
_J	Joule	_kph	Kilometers per hour
_K	Kelvin	_l	Liter
_Kcal	Kilocalorie	_lam	Lambert
_MHz	Megahertz	_lb	pound (16 oz)
_MW	Megawatt	_lbf	Pound-force
_MeV	Megaelectronvolt	_lbmol	Pound-mole
_N	Newton	_lbt	Troy pound
_Ohm	Ohm	_lep	Liter of oil equivalent
_P	Poise (measures viscosity)	_liqpt	US liquid pint (1 US gallon=8 US liquid pints)
_Pa	Pascal	_lm	Lumen
_R	Roentgen	_lx	Lux
_Rankine	Degree Rankine	_lyr	Light year
_S	Siemens	_m	Metre (unit)
_St	Stokes	_mho	Mho
_Sv	Sievert	_miUS	US statute mile
_T	Tesla	_mi^2	Square international mile.
_V	Volt	_mil	Mil
_W	Watt	_mile	International mile
_Wb	Weber	_mille	Nautical mile
_Wh	Watt-hour	_ml	millilitre
_a	Are (100 m2)	_mm	Millimetre
_acre	Acre	_mmHg	Millimeter of mercury (torr), 0 degree Celsius
_arcmin	Minute of arc	_mn	Minute
_arcs	Second of arc	_mol	Mole
_atm	Atmosphere	_mph	Miles per hour
_au	Astronomical unit	_oz	Ounce
_b	Barn	_ozUK	UK fluid ounce
_bar	Bar	_ozfl	US fluid ounce
_bbl	Barrel	_ozt	Troy ounce
_bblep	Barrel of oil equivalent	_pc	Parsec
_bu	Bushel (8 UK gallons)	_pdl	Poundal (force)
_buUS	American bushel	_ph	Phot
_cal	Calorie	_pk	US peck
_cd	Candela	_psi	Pounds per square inch
_chain	Chain (66 feet or 22 yards)	_ptUK	UK pint (1 UK gallon=8 UK pints)
_cm	Centimetre	_qt	Quart
_ct	Carat	_rad	Radian
_cu	US cup	_rd	Rad (0.01  Gy)
_d	Day	_rem	Rem
_dB	Decibel	_rod	Rod 1 (5.029215842 m)
_deg	Degree (angle)	_rpm	Revolutions per minute
_degreeF	Degree Fahrenheit	_s	Second
_dyn	Dyne	_s	second
_eV	Electron volt	_sb	Stilb
_erg	Erg	_slug	Slug
_fath	Fathom	_sr	Steradian
_fbm	Board foot	_st	Stere
_fc	Footcandle (≈ 10.764 lux)	_t	Metric ton
_fermi	Fermi	_tbsp	Tablespoon
_flam	Footlambert	_tec	Tonne of coal equivalent
_fm	Fathom	_tep	Tonne of oil equivalent
_ft	International foot	_tex	tex (10−6 kg/m)
_ftUS	Survey foot	_therm	EEC therm
_g	Gram	_ton	Short ton (2000 pounds)
_ga	Standard freefall	_tonUK	Long (UK) ton
_galC	Canadian gallon	_torr	Torr (mmHg)
_galUK	UK gallon	_tr	tour (2π rad)
_galUS	US gallon	_tsp	Teaspoon
_gf	Gram-force	_u	Atomic mass unit
_gmol	Gram-mole	_yd	International yard
_gon	Grade	_yr	Year
_grad	Grade	_h	Hour
_grain	Grain (≈ 0,0648 grams)	_µ	Micron

Table 24.1: Physical units in Xcas

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If a prefix is put before the unit then the unit is multiplied by a power of 10. For example, the prefix k or K, for kilo, indicates multiplication by 10³. See Table 24.2 for a list of the unit prefixes.

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Prefix	Name	(*10^) n	Prefix	Name	(*10^) n
Y	yota	24	d	deci	−1
Z	zeta	21	c	cent	−2
E	exa	18	m	mili	−3
P	peta	15	µ	micro	−6
T	tera	12	n	nano	−9
G	giga	9	p	pico	−12
M	mega	6	f	femto	−15
k or K	kilo	3	a	atto	−18
h or H	hecto	2	z	zepto	−21
D	deca	1	y	yocto	−24

Table 24.2: Unit prefixes in Xcas

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You cannot use a prefix with a built-in unit if the result gives another built-in unit.

For example, 1_a is one are, but 1_Pa is one pascal and not 10^15_a.

Examples

which is a unit object of value 10.5 meters.

which is a unit object of value 10.5 kilometers.