SI System¶

Namespace: mp_units::si

Module: mp_units.systems

Header: <mp-units/systems/si.h>

Secondary Headers:

<mp-units/systems/si/chrono.h>
<mp-units/systems/si/constants.h>
<mp-units/systems/si/math.h>
<mp-units/systems/si/prefixes.h>
<mp-units/systems/si/unit_symbols.h>
<mp-units/systems/si/units.h>

Units¶

Unit Name	Symbol	unit_symbol	Definition
`ampere`	A	`A`	`kind: isq::electric_current`
`becquerel`	Bq	`Bq`	`one / second kind: isq::activity`
`candela`	cd	`cd`	`kind: isq::luminous_intensity`
`coulomb`	C	`C`	`ampere * second`
`degree_Celsius`	℃ (`C)	`deg_C`	`kelvin origin: zeroth_degree_Celsius`
`farad`	F	`F`	`coulomb / volt`
`gram`	g	`g`	`kind: isq::mass`
`gray`	Gy	`Gy`	`joule / kilogram kind: isq::absorbed_dose`
`henry`	H	`H`	`weber / ampere`
`hertz`	Hz	`Hz`	`one / second kind: isq::frequency`
`joule`	J	`J`	`newton * metre`
`katal`	kat	`kat`	`mole / second`
`kelvin`	K	`K`	`kind: isq::thermodynamic_temperature origin: zeroth_kelvin`
`kilogram`	—	`kg`	`kilo<gram>`
`lumen`	lm	`lm`	`candela * steradian`
`lux`	lx	`lx`	`lumen / square(metre)`
`magnetic_constant`	μ₀ (u_0)	—	`mag<4> * mag_power<10, -7> * π * henry / metre`
`metre`	m	`m`	`kind: isq::length`
`mole`	mol	`mol`	`kind: isq::amount_of_substance`
`newton`	N	`N`	`kilogram * metre / square(second)`
`ohm`	Ω (ohm)	`Ω`, `ohm`	`volt / ampere`
`pascal`	Pa	`Pa`	`newton / square(metre)`
`radian`	rad	`rad`	`metre / metre kind: isq::angular_measure`
`second`	s	`s`	`kind: isq::duration`
`si2019::avogadro_constant`	N_A	—	`mag_ratio<602'214'076, 100'000'000> * mag_power<10, 23> / mole`
`si2019::boltzmann_constant`	k	—	`mag_ratio<1'380'649, 1'000'000> * mag_power<10, -23> * joule / kelvin`
`si2019::elementary_charge`	e	—	`mag_ratio<1'602'176'634, 1'000'000'000> * mag_power<10, -19> * coulomb`
`si2019::hyperfine_structure_transition_frequency_of_cs`	Δν_Cs (dv_Cs)	—	`mag<9'192'631'770> * hertz`
`si2019::luminous_efficacy`	K_cd	—	`mag<683> * lumen / watt`
`si2019::planck_constant`	h	—	`mag_ratio<662'607'015, 100'000'000> * mag_power<10, -34> * joule * second`
`si2019::speed_of_light_in_vacuum`	c	—	`mag<299'792'458> * metre / second`
`siemens`	S	`S`	`one / ohm`
`sievert`	Sv	`Sv`	`joule / kilogram kind: isq::dose_equivalent`
`standard_gravity`	g₀ (g_0)	—	`mag_ratio<980'665, 100'000> * metre / square(second)`
`steradian`	sr	`sr`	`square(metre) / square(metre) kind: isq::solid_angular_measure`
`tesla`	T	`T`	`weber / square(metre)`
`volt`	V	`V`	`watt / ampere`
`watt`	W	`W`	`joule / second`
`weber`	Wb	`Wb`	`volt * second`

Inline Namespaces

The mp_units::si::si2019 namespace is inline in mp_units::si, making its units directly accessible from the parent namespace.

Non-SI units accepted for use with the SI¶

Unit Name	Symbol	unit_symbol	Definition
`arcminute`	′ (')	`arcmin`	`mag_ratio<1, 60> * degree`
`arcsecond`	″ ('')	`arcsec`	`mag_ratio<1, 60> * arcminute`
`are`	a	`a`	`square(deca<metre>)`
`astronomical_unit`	au	`au`	`mag<149'597'870'700> * metre`
`dalton`	Da	`Da`	`mag_ratio<16'605'390'666'050, 10'000'000'000'000> * mag_power<10, -27> * kilogram`
`day`	d	`d`	`mag<24> * hour`
`degree`	° (deg)	`deg`	`mag_ratio<1, 180> * π * radian`
`electronvolt`	eV	`eV`	`mag_ratio<1'602'176'634, 1'000'000'000> * mag_power<10, -19> * joule`
`hectare`	—	`ha`	`hecto<are>`
`hour`	h	`h`	`mag<60> * minute`
`litre`	L	`l`, `L`	`cubic(deci<metre>)`
`minute`	min	`min`	`mag<60> * second`
`tonne`	t	`t`	`mag<1000> * kilogram`

Namespace

These units are defined in the mp_units::non_si namespace and are made available in the mp_units::si namespace through a using-directive.

Prefixes¶

Name	Symbol	Definition
`quecto`	q	`mag_power<10, -30>`
`ronto`	r	`mag_power<10, -27>`
`yocto`	y	`mag_power<10, -24>`
`zepto`	z	`mag_power<10, -21>`
`atto`	a	`mag_power<10, -18>`
`femto`	f	`mag_power<10, -15>`
`pico`	p	`mag_power<10, -12>`
`nano`	n	`mag_power<10, -9>`
`micro`	µ (u)	`mag_power<10, -6>`
`milli`	m	`mag_power<10, -3>`
`centi`	c	`mag_power<10, -2>`
`deci`	d	`mag_power<10, -1>`
`deca`	da	`mag_power<10, 1>`
`hecto`	h	`mag_power<10, 2>`
`kilo`	k	`mag_power<10, 3>`
`mega`	M	`mag_power<10, 6>`
`giga`	G	`mag_power<10, 9>`
`tera`	T	`mag_power<10, 12>`
`peta`	P	`mag_power<10, 15>`
`exa`	E	`mag_power<10, 18>`
`zetta`	Z	`mag_power<10, 21>`
`yotta`	Y	`mag_power<10, 24>`
`ronna`	R	`mag_power<10, 27>`
`quetta`	Q	`mag_power<10, 30>`

Point Origins¶

Name	Type	Definition
`absolute_zero`	absolute	`isq::thermodynamic_temperature`
`chrono_point_origin`	absolute	`isq::time`
`ice_point`	relative	`::mp_units::point<milli<kelvin>>(273'150)`
`zeroth_degree_Celsius`	—	alias to ice_point
`zeroth_kelvin`	—	alias to absolute_zero