Physical Constants Table

Constant	Symbol	Value	Units
Mean molecular weight of dry air	M_a	28.969	kg kmol⁻¹
Mean molecular weight of water	M_v	18.02	kg kmol⁻¹
Density of dry air at 101.325 kPa and 0 °C	-	1.293	kg m⁻³
Density of water at 4 °C	-	1000	kg m⁻³
Density of water at 20 °C	-	998.23	kg m⁻³
Barometric pressure at standard temperature and pressure	-	101.325	kPa
Standard temperature and pressure (STP)	-	0 °C at 101.325 kPa	(also known as normal temperature and pressure)
Universal gas constant	R_gas = MR	8.3143	J mol⁻¹ K⁻¹
Volume of 1 mol of the permanent gases (at 101.325 kPa and 0 °C)	-	22.4136	m³
Characteristic gas constant for dry air	R_a	287	J kg⁻¹ K⁻¹
Characteristic gas constant for steam	R_v	462	J kg⁻¹ K⁻¹
Mean specific heat of air at constant pressure	c_pa	1005	J kg⁻¹ K⁻¹
Mean specific heat of air at constant volume	c_va	718	J kg⁻¹ K⁻¹
Mean specific heat of steam at constant pressure	c_pv	4210	J kg⁻¹ K⁻¹
Mean specific heat of steam at constant volume	c_vv	1810	J kg⁻¹ K⁻¹
Adiabatic index for air at room temperature and pressure	-	1.4	-
Latent heat of steam at 0 °C	-	2500	kJ kg⁻¹
Standard gravity	-	9.80665	m s⁻²
Velocity of sound in air at normal temperature and pressure	c	331.46	m s⁻¹
Stefan's Constant	σ	5.67 × 10⁻⁸	W m⁻² K⁴