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Constants

Every physical and engineering constant the engine reasons with, stored canonically in SI and quoted in English units wherever a textbook does. Looking for units and conversions instead? Units.

25 constants

Conversion

Constant	Symbol	SI value	English value	Dimension	Notes
Ton of refrigeration	1 ton	3516.853 W	12000 Btu/h	M·L²·T⁻³	Standard refrigeration capacity unitCengel Ch. 11

Electromagnetism

Constant	Symbol	SI value	English value	Dimension	Notes
Elementary charge	e	1.60217663 × 10⁻¹⁹ C	—	T·I	Exact (SI definition)CODATA
Faraday constant	F	9.64853321 × 10⁷ C/kmol	—	T·N⁻¹·I	96485.33212 C/molCODATA
Vacuum permeability	mu₀	1.25663706 × 10⁻⁶ H/m	—	M·L·T⁻²·I⁻²	Magnetic couplingCODATA
Vacuum permittivity	eps₀	8.85418781 × 10⁻¹² F/m	—	M⁻¹·L⁻³·T⁴·I²	Electrostatic and MEMS couplingCODATA

Heat transfer

Constant	Symbol	SI value	English value	Dimension	Notes
Stefan-Boltzmann constant	sigma	5.67037442 × 10⁻⁸ W/m²·K⁴	1.714 × 10⁻⁹ Btu/h·ft²·R⁴	M·T⁻³·K⁻⁴	Blackbody emissive powerCengel Ch. 12

Mechanics

Constant	Symbol	SI value	English value	Dimension	Notes
Gravitational conversion constant	g_c	1 kg·m/N·s²	32.174 lbm·ft/lbf·s²	dimensionless	Unity in SI; needed in English engineering unitsMoran Sec. 1.6
Standard gravitational acceleration	g	9.80665 m/s²	32.174 ft/s²	L·T⁻²	Standard sea-level valueMoran / Cengel front matter

Thermodynamics

Constant	Symbol	SI value	English value	Dimension	Notes
Constant-volume specific heat of air at 300 K	cᵥ	718 J/kg·K	0.171 Btu/lbm·R	L²·T⁻²·K⁻¹	Cold-air-standard valueCengel Table A-2
Density of liquid water at 4 °C	rho	1000 kg/m³	62.43 lbm/ft³	M·L⁻³	Reference densityCengel Table A-3
Gas constant of air	Rₐᵢᵣ	287 J/kg·K	0.06855 Btu/lbm·R	L²·T⁻²·K⁻¹	R_u / M_air, M_air = 28.97 kg/kmolMoran Table A-20
Gas constant of water vapor	Rᵥ	461.5 J/kg·K	0.1102 Btu/lbm·R	L²·T⁻²·K⁻¹	M = 18.015 kg/kmolMoran Table A-1
Ice point	T₀	273.15 K	491.67 R	K	0 °C = 32 °FCengel Ch. 1
Latent heat of vaporization of water at 100 °C	h_fg	2.257 × 10⁶ J/kg	970.1 Btu/lbm	L²·T⁻²	At 101.325 kPaMoran Table A-2
Molar mass of air	Mₐᵢᵣ	28.97 kg/kmol	28.97 lbm/lbmol	M·N⁻¹	Dry airMoran Table A-1
Specific heat of air at 300 K	cₚ	1005 J/kg·K	0.24 Btu/lbm·R	L²·T⁻²·K⁻¹	Cold-air-standard valueCengel Table A-2
Specific heat ratio of air	k	1.4 -	—	dimensionless	c_p/c_v at 300 KCengel Table A-2
Standard atmospheric pressure	Pₐₜₘ	101325 Pa	14.696 psia	M·L⁻¹·T⁻²	1 atm = 1.01325 bar = 760 mmHgMoran front matter
Standard reference temperature	T_ref	298.15 K	536.67 R	K	25 °C = 77 °F, reference state for formation enthalpiesMoran Ch. 13
Triple-point temperature of water	Tₜₚ	273.16 K	491.688 R	K	At 0.6117 kPaMoran Table A-2
Universal gas constant	Rᵤ	8314.46262 J/kmol·K	1.98588 Btu/lbmol·R	M·L²·T⁻²·K⁻¹·N⁻¹	8.314462618 kJ/kmol·K = 1545.37 ft·lbf/lbmol·RMoran Table A-1 / Cengel

Universal

Constant	Symbol	SI value	English value	Dimension	Notes
Avogadro constant	N_A	6.02214076 × 10²⁶ 1/kmol	—	N⁻¹	6.02214076e23 1/mol, exactCODATA
Boltzmann constant	k_B	1.380649 × 10⁻²³ J/K	—	M·L²·T⁻²·K⁻¹	Exact (SI definition)CODATA
Planck constant	h	6.62607015 × 10⁻³⁴ J·s	—	M·L²·T⁻¹	Exact (SI definition)CODATA
Speed of light in vacuum	c	2.99792458 × 10⁸ m/s	—	L·T⁻¹	Exact (SI definition)CODATA