KasperCalc: Air Pressure from Altitude

Air Pressure vs Altitude Chart

Density and specific volume of air varies with elevation above sea level.

The density of air varies with pressure (the Ideal Gas Law) and the altitude above sea level. Mean absolute pressure at sea level is approximately 760 mmHg (101.325 kPa, kN/m2) with a variation is about +/- 5%.

Based on the International Standard Atmosphere (ISA) model. Sea level: 14.696 PSI (101.325 kPa / 760.0 mmHg).

Troposphere extends to 36,089 ft (11,000 m). Stratosphere extends to 65,617 ft (20,000 m). Negative altitudes are below sea level.

Toggle data sets by clicking the legend.

Air Pressure Calculator

Select Input Unit:

Altitude (ft):

mmHg:

kPa:

Pa:

PSIG (ref. sea level):

Result (PSIA):

Also See:

Water Density Calculator

STP and NTP

STP — Standard Temperature and Pressure

STP is defined as 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10⁵ Pa (100 kPa, 1 bar) — according to IUPAC (International Union of Pure and Applied Chemistry), since 1982.

NTP — Normal Temperature and Pressure

NTP is defined as 293.15 K (20 °C, 68 °F) and an absolute pressure of 1 atm (101,325 Pa, 101.325 kPa, 14.696 PSI) — according to NIST (National Institute of Standards and Technology). NTP is commonly used for testing and documentation of fan capacities.

Note! — Other definitions of STP and NTP are widely used.

Altitude and Specific Volume Correction

The specific volume of standard air at a certain altitude can be calculated by multiplying the sea-level specific volume by the volume correction factor below.

Volume correction factor relative to standard sea-level conditions (0 ft).

Air — Volume Correction vs. Altitude

Altitude (m)	Altitude (ft)	Volume Correction Factor
0	0	1.00
480	1,600	1.05
990	3,300	1.11
1,500	5,000	1.17
1,980	6,600	1.24
2,460	8,200	1.31
2,970	9,900	1.39

Temperature vs. Elevation Density Correction

Density correction factor relative to sea level at 70 °F.
Each line represents a constant air temperature. Toggle lines by clicking the legend.

Using the Density Correction Factor

The chart above can be used to estimate the temperature vs. elevation density correction factor. The air density at a given temperature and elevation can then be calculated as:

ρ = ρ_ref / f (1)

where:

ρ = density at the given temperature and elevation (lbm/ft³)
ρ_ref = reference density at 0 ft elevation and 70 °F — 0.075 lbm/ft³
f = correction factor read from the chart above

Example — Density at 5,000 ft Elevation and 200 °F

From the chart above, at an elevation of 5,000 ft and an air temperature of 200 °F, the correction factor is approximately 1.5. The density can be calculated as:

ρ = (0.075 lbm/ft³) / 1.5

= 0.050 lbm/ft³

Note! This calculation assumes dry air and standard ISA pressure at the given altitude. Humidity and non-standard pressure conditions will affect the actual density.

Altitude and Air Pressure — Reference Table

Air — Pressure vs. Altitude

Altitude (ft)	Altitude (m)	inHg	Torr	PSIA	kPa
0	0	29.92	759.97	14.70	101.3
500	152	29.39	746.51	14.43	99.4
1,000	305	28.86	733.04	14.17	97.6
1,500	457	28.34	719.84	13.91	95.8
2,000	610	27.82	706.63	13.66	94.1
2,500	762	27.32	693.93	13.41	92.4
3,000	914	26.82	681.23	13.17	90.7
3,500	1,067	26.33	668.78	12.93	89.1
4,000	1,219	25.84	656.34	12.69	87.4
4,500	1,372	25.37	644.40	12.46	85.8
5,000	1,524	24.90	632.46	12.23	84.3
5,500	1,676	24.44	620.78	12.00	82.7
6,000	1,829	23.98	609.09	11.77	81.1
6,500	1,981	23.53	597.66	11.55	79.6
7,000	2,134	23.09	586.49	11.34	78.1
7,500	2,286	22.66	575.56	11.13	76.7
8,000	2,438	22.23	564.64	10.91	75.2
8,500	2,591	21.81	553.97	10.71	73.8
9,000	2,743	21.39	543.31	10.50	72.3
9,500	2,896	20.98	532.89	10.30	71.0
10,000	3,048	20.58	522.73	10.10	69.6
10,500	3,200	20.19	512.83	9.91	68.3
11,000	3,353	19.80	502.92	9.72	67.0
11,500	3,505	19.41	493.01	9.53	65.7
12,000	3,658	19.03	483.36	9.34	64.4
12,500	3,810	18.66	473.96	9.16	63.1
13,000	3,962	18.30	464.82	8.99	61.9
13,500	4,115	17.94	455.68	8.81	60.7
14,000	4,267	17.58	446.53	8.63	59.5
14,500	4,420	17.24	437.90	8.46	58.3
15,000	4,572	16.89	429.01	8.29	57.1
15,500	4,724	16.56	420.62	8.13	56.0
16,000	4,877	16.22	411.99	7.96	54.8
16,500	5,029	15.90	403.86	7.81	53.8
17,000	5,182	15.58	395.73	7.65	52.7
17,500	5,334	15.26	387.60	7.47	51.5
18,000	5,486	14.95	379.73	7.34	50.6
18,500	5,639	14.65	372.11	7.19	49.5
19,000	5,791	14.35	364.49	7.05	48.6
19,500	5,944	14.05	356.87	6.90	47.5
20,000	6,096	13.76	349.50	6.76	46.6
20,500	6,248	13.48	342.39	6.62	45.6
21,000	6,401	13.20	335.28	6.48	44.6
21,500	6,553	12.92	328.17	6.34	43.7
22,000	6,706	12.65	321.31	6.21	42.8
22,500	6,858	12.38	314.45	6.08	41.9
23,000	7,010	12.12	307.85	5.95	41.0
23,500	7,163	11.86	301.24	5.82	40.1
24,000	7,315	11.61	294.89	5.70	39.3
24,500	7,468	11.36	288.54	5.58	38.4
25,000	7,620	11.12	282.45	5.46	37.6
25,500	7,772	10.88	276.35	5.34	36.8
26,000	7,925	10.64	270.26	5.22	36.0
26,500	8,077	10.41	264.41	5.11	35.2
27,000	8,230	10.18	258.57	5.00	34.5
27,500	8,382	9.96	252.98	4.89	33.7
28,000	8,534	9.74	247.40	4.78	32.9
28,500	8,687	9.53	242.06	4.68	32.2
29,000	8,839	9.31	236.47	4.57	31.5
29,500	8,992	9.11	231.39	4.47	30.8
30,000	9,144	8.90	226.06	4.37	30.1