International Standard Atmosphere

A model of the ICAO International Standard Atmosphere, based upon the US Standard Atmosphere 1976.
Validated up to 85Km.
A couple of useful rules of thumb can be seen at the lower atmospheric levels.
  • 1" pressure decrease per 1000ft, so you can expect to lose 1" per 1000ft
    once at wide open throttle on a normally aspirated piston engine.
  • Pressure decreases .5PSI per 1000ft appoximately.
Altitude
Feet
Z
M
Temp
°C
Pressure
mb
Pressure inHGPressue PSIPressure RatioDensity
KG Per M3
Density RatioC
Kt
Altitude
(Meters)
-1,000 -305 16.98 1,050.41 31.02 15.23 1.0367 1.261 1.0296 663 -305
0 0 15.00 1,013.25 29.92 14.70 1.0000 1.225 1.0000 661 0
1,000 305 13.02 977.17 28.85 14.17 0.9644 1.190 0.9711 659 305
2,000 610 11.04 942.13 27.82 13.66 0.9298 1.155 0.9428 656 610
3,000 915 9.06 908.12 26.82 13.17 0.8962 1.121 0.9152 654 914
4,000 1,219 7.08 875.11 25.84 12.69 0.8637 1.088 0.8881 652 1,219
5,000 1,524 5.09 843.07 24.89 12.23 0.8320 1.056 0.8617 650 1,524
6,000 1,829 3.11 812.00 23.98 11.78 0.8014 1.024 0.8359 647 1,829
7,000 2,134 1.13 781.85 23.09 11.34 0.7716 0.993 0.8107 645 2,134
8,000 2,439 -0.85 752.62 22.22 10.92 0.7428 0.963 0.7861 643 2,438
9,000 2,744 -2.83 724.29 21.39 10.50 0.7148 0.933 0.7620 640 2,743
10,000 3,049 -4.81 696.82 20.58 10.11 0.6877 0.905 0.7385 638 3,048
11,000 3,355 -6.79 670.20 19.79 9.72 0.6614 0.877 0.7156 636 3,353
12,000 3,660 -8.77 644.41 19.03 9.35 0.6360 0.849 0.6932 633 3,658
13,000 3,965 -10.76 619.43 18.29 8.98 0.6113 0.822 0.6714 631 3,962
14,000 4,270 -12.74 595.24 17.58 8.63 0.5875 0.796 0.6501 628 4,267
15,000 4,575 -14.72 571.82 16.89 8.29 0.5643 0.771 0.6293 626 4,572
16,000 4,881 -16.70 549.15 16.22 7.96 0.5420 0.746 0.6090 624 4,877
17,000 5,186 -18.68 527.22 15.57 7.65 0.5203 0.722 0.5892 621 5,182
18,000 5,491 -20.66 506.00 14.94 7.34 0.4994 0.698 0.5699 619 5,486
19,000 5,796 -22.64 485.48 14.34 7.04 0.4791 0.675 0.5511 616 5,791
20,000 6,102 -24.62 465.63 13.75 6.75 0.4595 0.653 0.5328 614 6,096
21,000 6,407 -26.61 446.45 13.18 6.48 0.4406 0.631 0.5150 611 6,401
22,000 6,713 -28.59 427.91 12.64 6.21 0.4223 0.610 0.4976 609 6,706
23,000 7,018 -30.57 410.01 12.11 5.95 0.4046 0.589 0.4807 607 7,010
24,000 7,324 -32.55 392.71 11.60 5.70 0.3876 0.569 0.4642 604 7,315
25,000 7,629 -34.53 376.01 11.10 5.45 0.3711 0.549 0.4481 602 7,620
26,000 7,935 -36.51 359.89 10.63 5.22 0.3552 0.530 0.4325 599 7,925
27,000 8,240 -38.49 344.33 10.17 4.99 0.3398 0.511 0.4173 597 8,230
28,000 8,546 -40.47 329.32 9.72 4.78 0.3250 0.493 0.4025 594 8,534
29,000 8,852 -42.45 314.85 9.30 4.57 0.3107 0.475 0.3881 591 8,839
30,000 9,157 -44.44 300.90 8.89 4.36 0.2970 0.458 0.3741 589 9,144
31,000 9,463 -46.42 287.45 8.49 4.17 0.2837 0.442 0.3605 586 9,449
32,000 9,769 -48.40 274.49 8.11 3.98 0.2709 0.425 0.3473 584 9,754
33,000 10,074 -50.38 262.01 7.74 3.80 0.2586 0.410 0.3345 581 10,058
34,000 10,380 -52.36 249.99 7.38 3.63 0.2467 0.394 0.3220 579 10,363
35,000 10,686 -54.34 238.42 7.04 3.46 0.2353 0.380 0.3099 576 10,668
36,000 10,992 -56.32 227.29 6.71 3.30 0.2243 0.365 0.2981 573 10,973
36,089 11,019 -56.50 226.32 6.68 3.28 0.2234 0.364 0.2971 573 11,000
37,000 11,298 -56.50 216.63 6.40 3.14 0.2138 0.348 0.2844 573 11,278
38,000 11,604 -56.50 206.46 6.10 2.99 0.2038 0.332 0.2710 573 11,582
39,000 11,909 -56.50 196.77 5.81 2.85 0.1942 0.316 0.2583 573 11,887
40,000 12,215 -56.50 187.54 5.54 2.72 0.1851 0.302 0.2462 573 12,192
41,000 12,521 -56.50 178.74 5.28 2.59 0.1764 0.287 0.2346 573 12,497
42,000 12,827 -56.50 170.35 5.03 2.47 0.1681 0.274 0.2236 573 12,802
43,000 13,133 -56.50 162.36 4.79 2.35 0.1602 0.261 0.2131 573 13,106
44,000 13,440 -56.50 154.74 4.57 2.24 0.1527 0.249 0.2031 573 13,411
45,000 13,746 -56.50 147.48 4.35 2.14 0.1455 0.237 0.1936 573 13,716
46,000 14,052 -56.50 140.56 4.15 2.04 0.1387 0.226 0.1845 573 14,021
47,000 14,358 -56.50 133.96 3.96 1.94 0.1322 0.215 0.1758 573 14,326
48,000 14,664 -56.50 127.67 3.77 1.85 0.1260 0.205 0.1676 573 14,630
49,000 14,970 -56.50 121.68 3.59 1.76 0.1201 0.196 0.1597 573 14,935
50,000 15,277 -56.50 115.97 3.42 1.68 0.1145 0.186 0.1522 573 15,240
51,000 15,583 -56.50 110.53 3.26 1.60 0.1091 0.178 0.1451 573 15,545
52,000 15,889 -56.50 105.34 3.11 1.53 0.1040 0.169 0.1383 573 15,850
53,000 16,196 -56.50 100.40 2.96 1.46 0.0991 0.161 0.1318 573 16,154
54,000 16,502 -56.50 95.69 2.83 1.39 0.0944 0.154 0.1256 573 16,459
55,000 16,808 -56.50 91.20 2.69 1.32 0.0900 0.147 0.1197 573 16,764
56,000 17,115 -56.50 86.92 2.57 1.26 0.0858 0.140 0.1141 573 17,069
57,000 17,421 -56.50 82.84 2.45 1.20 0.0818 0.133 0.1087 573 17,374
58,000 17,728 -56.50 78.95 2.33 1.15 0.0779 0.127 0.1036 573 17,678
59,000 18,034 -56.50 75.25 2.22 1.09 0.0743 0.121 0.0988 573 17,983
60,000 18,341 -56.50 71.72 2.12 1.04 0.0708 0.115 0.0941 573 18,288
61,000 18,647 -56.50 68.35 2.02 0.99 0.0675 0.110 0.0897 573 18,593
62,000 18,954 -56.50 65.14 1.92 0.94 0.0643 0.105 0.0855 573 18,898
63,000 19,261 -56.50 62.09 1.83 0.90 0.0613 0.100 0.0815 573 19,202
64,000 19,567 -56.50 59.17 1.75 0.86 0.0584 0.095 0.0777 573 19,507
65,000 19,874 -56.50 56.40 1.67 0.82 0.0557 0.091 0.0740 573 19,812
65,617 20,063 -56.50 54.75 1.62 0.79 0.0540 0.088 0.0719 573 20,000
68,898 21,070 -55.50 46.78 1.38 0.68 0.0462 0.075 0.0611 575 21,000
72,178 22,076 -54.50 40.00 1.18 0.58 0.0395 0.064 0.0520 576 22,000
75,459 23,084 -53.50 34.22 1.01 0.50 0.0338 0.054 0.0443 577 23,000
78,740 24,091 -52.50 29.30 0.87 0.43 0.0289 0.046 0.0378 578 24,000
82,021 25,099 -51.50 25.11 0.74 0.36 0.0248 0.039 0.0322 580 25,000
85,302 26,107 -50.50 21.53 0.64 0.31 0.0212 0.034 0.0275 581 26,000
88,583 27,115 -49.50 18.47 0.55 0.27 0.0182 0.029 0.0235 582 27,000
91,864 28,124 -48.50 15.86 0.47 0.23 0.0157 0.025 0.0201 584 28,000
95,144 29,133 -47.50 13.63 0.40 0.20 0.0135 0.021 0.0172 585 29,000
98,425 30,142 -46.50 11.72 0.35 0.17 0.0116 0.018 0.0147 586 30,000
101,706 31,152 -45.50 10.08 0.30 0.15 0.0100 0.015 0.0126 588 31,000
104,987 32,162 -44.50 8.68 0.26 0.13 0.0086 0.013 0.0108 589 32,000