Specific Heat of Air (Cp, Cv): Calculator & Chart

Air Specific Heat (cp and cv) Chart

Specific heat capacity cp and cv of dry air vs temperature in degrees Fahrenheit at 1 atm, 10 bar and 100 bar

Dry air, calculated with CoolProp 7.2.0. Solid lines are cp. Dotted lines are cv (same colour, same pressure). The cp curves at 10 and 100 bar rise at low temperature because of real-gas effects.

Air Ratio of Specific Heats (γ) Chart

Ratio of specific heats gamma of dry air vs temperature in degrees Fahrenheit at 1 atm, 10 bar and 100 bar

γ = cp/cv for dry air. It is 1.40 near room temperature and falls to about 1.3 at 1000 °C.

Air Specific Heat Calculator

Degrees (°F):

Degrees (°C):

Pressure:

Specific heat at constant pressure, cp

cp (J/(kg·K)):

cp (kJ/(kg·K)):

cp (Btu/(lb·°F)):

Molar cp (J/(mol·K)):

Specific heat at constant volume, cv

cv (J/(kg·K)):

cv (kJ/(kg·K)):

cv (Btu/(lb·°F)):

Ratio of specific heats

γ = cp/cv:

cp − cv (J/(kg·K)):

Dry air, absolute pressure. Range: −100 to 1000 °C (−148 to 1832 °F) and 1 atm to 100 bar (14.696 to 1450 psia). Outside it the calculator shows “Out of Range”. Values are interpolated linearly in temperature (10 °C grid) and in ln P between 1 atm, 2, 5, 10, 20, 50 and 100 bar. Interpolation adds about 0.1 % at most (checked against CoolProp at six off-grid points).

Specific Heat of Air

Quick answer

Dry air at 20 °C and 1 atm has cp = 1006.1 J/(kg·K) (0.2403 Btu/(lb·°F)), cv = 717.67 J/(kg·K) and γ = 1.402. At 1000 °C and 1 atm, cp is 1184.7 J/(kg·K) and γ is 1.320. This page is for dry air.

What cp, cv and γ mean

cp is the heat needed to raise one kilogram of air by one kelvin at constant pressure. cv is the same at constant volume. Their ratio is γ:

γ = cp / cv

For an ideal gas, cp − cv = R = 287.05 J/(kg·K). The table shows that real air stays close to this at 1 atm. Use cp for heating air in a duct or heat exchanger (see LMTD calculator). Use γ for the speed of sound (see speed of sound of air), nozzle flow and compression work.

Pressure effect

At 1 atm, cp changes by about 17 % from −100 to 1000 °C. Pressure matters more at high pressure and low temperature. At 100 bar and −100 °C, cp is 2358.6 J/(kg·K), against 1008.8 J/(kg·K) at 1 atm.

Where the numbers come from

Accuracy. Lemmon et al. (2000) state an uncertainty of about 0.1 % in density, 0.2 % in speed of sound and 1 % in heat capacity from the solidification point to 873 K (600 °C) and up to 70 MPa. Above 873 K there were no reliable air data, so nitrogen data were used and the paper gives about 0.5 % for density. Lemmon & Jacobsen (2004) state about 5 % for the viscosity and thermal conductivity of air, and more near the critical point. Viscosity and conductivity above about 600 °C, and the 1000 °C end of the range, are less certain than that. CoolProp uses a molar mass of 28.96546 g/mol, the U.S. Standard Atmosphere uses 28.9644 g/mol. That is the main reason CoolProp density at 15 °C and 1 atm is 0.04 % above the Standard Atmosphere value.

Dry Air Specific Heat at 1 atm (101.325 kPa)

cp, cv and γ of dry air every 20 °C from −100 to 1000 °C at 1 atm.

Temp (°C)	Temp (°F)	cp (J/(kg·K))	cp (Btu/(lb·°F))	cv (J/(kg·K))	cv (Btu/(lb·°F))	γ
-100.0	-148.0	1008.8	0.2409	716.59	0.1712	1.408
-80.00	-112.0	1007.2	0.2406	716.23	0.1711	1.406
-60.00	-76.00	1006.2	0.2403	716.11	0.1710	1.405
-40.00	-40.00	1005.7	0.2402	716.19	0.1711	1.404
-20.00	-4.000	1005.5	0.2402	716.46	0.1711	1.403
0	32.00	1005.7	0.2402	716.95	0.1712	1.403
20.00	68.00	1006.1	0.2403	717.67	0.1714	1.402
40.00	104.0	1006.9	0.2405	718.65	0.1716	1.401
60.00	140.0	1008.0	0.2408	719.92	0.1719	1.400
80.00	176.0	1009.5	0.2411	721.49	0.1723	1.399
100.0	212.0	1011.2	0.2415	723.38	0.1728	1.398
120.0	248.0	1013.3	0.2420	725.58	0.1733	1.397
140.0	284.0	1015.8	0.2426	728.10	0.1739	1.395
160.0	320.0	1018.5	0.2433	730.93	0.1746	1.393
180.0	356.0	1021.6	0.2440	734.06	0.1753	1.392
200.0	392.0	1025.0	0.2448	737.46	0.1761	1.390
220.0	428.0	1028.6	0.2457	741.11	0.1770	1.388
240.0	464.0	1032.4	0.2466	745.00	0.1779	1.386
260.0	500.0	1036.5	0.2476	749.09	0.1789	1.384
280.0	536.0	1040.7	0.2486	753.36	0.1799	1.381
300.0	572.0	1045.1	0.2496	757.77	0.1810	1.379
320.0	608.0	1049.6	0.2507	762.32	0.1821	1.377
340.0	644.0	1054.2	0.2518	766.96	0.1832	1.375
360.0	680.0	1059.0	0.2529	771.68	0.1843	1.372
380.0	716.0	1063.7	0.2541	776.46	0.1855	1.370
400.0	752.0	1068.5	0.2552	781.27	0.1866	1.368
420.0	788.0	1073.3	0.2564	786.10	0.1878	1.365
440.0	824.0	1078.1	0.2575	790.92	0.1889	1.363
460.0	860.0	1082.9	0.2587	795.73	0.1901	1.361
480.0	896.0	1087.7	0.2598	800.51	0.1912	1.359
500.0	932.0	1092.4	0.2609	805.24	0.1923	1.357
520.0	968.0	1097.1	0.2620	809.93	0.1934	1.355
540.0	1004	1101.7	0.2631	814.55	0.1946	1.353
560.0	1040	1106.3	0.2642	819.11	0.1956	1.351
580.0	1076	1110.7	0.2653	823.59	0.1967	1.349
600.0	1112	1115.1	0.2663	827.99	0.1978	1.347
620.0	1148	1119.5	0.2674	832.31	0.1988	1.345
640.0	1184	1123.7	0.2684	836.55	0.1998	1.343
660.0	1220	1127.8	0.2694	840.69	0.2008	1.342
680.0	1256	1131.9	0.2703	844.75	0.2018	1.340
700.0	1292	1135.8	0.2713	848.71	0.2027	1.338
720.0	1328	1139.7	0.2722	852.58	0.2036	1.337
740.0	1364	1143.5	0.2731	856.36	0.2045	1.335
760.0	1400	1147.2	0.2740	860.05	0.2054	1.334
780.0	1436	1150.8	0.2749	863.64	0.2063	1.332
800.0	1472	1154.2	0.2757	867.15	0.2071	1.331
820.0	1508	1157.7	0.2765	870.57	0.2079	1.330
840.0	1544	1161.0	0.2773	873.90	0.2087	1.329
860.0	1580	1164.2	0.2781	877.15	0.2095	1.327
880.0	1616	1167.4	0.2788	880.31	0.2103	1.326
900.0	1652	1170.5	0.2796	883.39	0.2110	1.325
920.0	1688	1173.5	0.2803	886.39	0.2117	1.324
940.0	1724	1176.4	0.2810	889.31	0.2124	1.323
960.0	1760	1179.2	0.2817	892.16	0.2131	1.322
980.0	1796	1182.0	0.2823	894.93	0.2138	1.321
1000	1832	1184.7	0.2830	897.64	0.2144	1.320

Calculated with CoolProp 7.2.0. 1 Btu/(lb·°F) = 4186.8 J/(kg·K).

Dry Air Specific Heat at 1 atm, 10 bar and 100 bar

At selected temperatures and three pressures.

Temp (°C)	Temp (°F)	Pressure (bara)	Pressure (psia)	cp (J/(kg·K))	cp (Btu/(lb·°F))	cv (J/(kg·K))	cv (Btu/(lb·°F))	γ
1 bara (1 atm, 14.7 psia)
-100	-148.0	1.013	14.7	1008.8	0.2409	716.59	0.1712	1.408
0	32.00	1.013	14.7	1005.7	0.2402	716.95	0.1712	1.403
100	212.0	1.013	14.7	1011.2	0.2415	723.38	0.1728	1.398
200	392.0	1.013	14.7	1025.0	0.2448	737.46	0.1761	1.390
400	752.0	1.013	14.7	1068.5	0.2552	781.27	0.1866	1.368
600	1112	1.013	14.7	1115.1	0.2663	827.99	0.1978	1.347
800	1472	1.013	14.7	1154.2	0.2757	867.15	0.2071	1.331
1000	1832	1.013	14.7	1184.7	0.2830	897.64	0.2144	1.320
10 bara (145 psia)
-100	-148.0	10	145	1072.6	0.2562	728.93	0.1741	1.471
0	32.00	10	145	1023.7	0.2445	719.71	0.1719	1.422
100	212.0	10	145	1019.7	0.2435	724.69	0.1731	1.407
200	392.0	10	145	1029.8	0.2460	738.29	0.1763	1.395
400	752.0	10	145	1070.7	0.2557	781.74	0.1867	1.370
600	1112	10	145	1116.3	0.2666	828.31	0.1978	1.348
800	1472	10	145	1155.0	0.2759	867.38	0.2072	1.332
1000	1832	10	145	1185.2	0.2831	897.82	0.2144	1.320
100 bara (1450 psia)
-100	-148.0	100	1450	2358.6	0.5633	844.03	0.2016	2.794
0	32.00	100	1450	1210.6	0.2892	745.27	0.1780	1.624
100	212.0	100	1450	1098.5	0.2624	736.99	0.1760	1.491
200	392.0	100	1450	1074.0	0.2565	746.14	0.1782	1.439
400	752.0	100	1450	1090.2	0.2604	786.18	0.1878	1.387
600	1112	100	1450	1127.0	0.2692	831.35	0.1986	1.356
800	1472	100	1450	1161.5	0.2774	869.66	0.2077	1.336
1000	1832	100	1450	1189.5	0.2841	899.62	0.2149	1.322

The calculator above covers 2, 5, 20 and 50 bar as well.

Related Air Pages and Tools

Compare with water specific heat. Heat load = mass flow × cp × ΔT. Mass flow of air comes from gas mass flow rate or pipe velocity.

Sources

E. W. Lemmon, R. T. Jacobsen, S. G. Penoncello and D. G. Friend, “Thermodynamic Properties of Air and Mixtures of Nitrogen, Argon, and Oxygen From 60 to 2000 K at Pressures to 2000 MPa,” J. Phys. Chem. Ref. Data 29(3), 331–385, 2000. doi:10.1063/1.1285884. Equation of state for dry air: density, specific heats, speed of sound, compressibility factor. Opened the NIST reprint, accessed 25 Oct 2026.
E. W. Lemmon and R. T. Jacobsen, “Viscosity and Thermal Conductivity Equations for Nitrogen, Oxygen, Argon, and Air,” Int. J. Thermophys. 25(1), 21–69, 2004. doi:10.1023/B:IJOT.0000022327.04529.f3. Viscosity and thermal conductivity of air. Only the abstract was read (NIST publication page), accessed 25 Oct 2026.
I. H. Bell, J. Wronski, S. Quoilin and V. Lemort, “Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp,” Ind. Eng. Chem. Res. 53(6), 2498–2508, 2014. doi:10.1021/ie4033999. The software used (CoolProp 7.2.0, fluid “Air”) to evaluate the two correlations above.
NOAA, NASA and USAF, U.S. Standard Atmosphere, 1976, NASA-TM-X-74335. ntrs.nasa.gov/citations/19770009539. Sea-level reference values, dry-air composition and Sutherland constants, accessed 25 Oct 2026.

All numbers on this page are calculated, not measured here. See the Air General Properties page for the accuracy statements and the cross-check against the U.S. Standard Atmosphere.

Specific Heat of Air (cp, cv and gamma) Calculator and Chart

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