Specific heat capacity of dry air
| Value | 1,005 J/(kg·K) |
| Status | Conventional / typical value |
| Source | NIST Chemistry WebBook; ASHRAE Handbook-Fundamentals |
| Categories | ThermodynamicEngineering & Trade |
Specific heat capacity of dry air in every specific heat capacity unit
| joule per kilogram-kelvin | 1,005 J/(kg·K) |
| joule per kilogram-Celsius | 1,005 J/(kg·°C) |
| foot pound-force per pound-Rankine | 186.79185 ft·lbf/(lb·°R) |
| kilojoule per kilogram-kelvin | 1.005 kJ/(kg·K) |
| kilojoule per kilogram-Celsius | 1.005 kJ/(kg·°C) |
| joule per gram-kelvin | 1.005 J/(g·K) |
| calorie per gram-Celsius | 0.24020076 cal/(g·°C) |
| kilocalorie per kilogram-Celsius | 0.24020076 kcal/(kg·°C) |
| BTU per pound-Fahrenheit | 0.24004013 BTU/(lb·°F) |
| BTU per pound-Rankine | 0.24004013 BTU/(lb·°R) |
Learning zone
This is the constant behind every air-side heat calculation. Combined with a density of 1.2 kg/m³ it produces the familiar shortcuts: 1.2 kW per m³/s per kelvin in SI, or the North American sensible heat factor of 1.08 in Q = 1.08 × cfm × ΔT BTU/h, which quietly bundles specific heat, standard air density and the minutes-to-hours conversion into one number.
Dry air's cp is nearly constant near ambient — 1005 J/(kg·K) at 300 K, rising only to about 1014 at 400 K — so treating it as fixed is safe for HVAC. Moist air is different: because water vapour's cp is roughly 1.86 kJ/(kg·K), psychrometric work uses the moist-air value cp + 1.86W per kilogram of dry air, and at typical humidity ratios that adds one to two percent.