If you know the atmoshperic pressure of your rocket flight at apogee, this table gives you a good estimation of altitude above sea level. If you are above sea level (as most of us are), simply subtracting your elevation from the altitude gives a close approximation. Should be accurate to within 150' or so.
| Feet | Pressure [mb] |
Feet | Pressure [mb] |
| 1000 | 977.1657 | 10900 | 672.8221 |
| 1100 | 973.6153 | 11000 | 670.1978 |
| 1200 | 970.0753 | 11100 | 667.5819 |
| 1300 | 966.5458 | 11200 | 664.9743 |
| 1400 | 963.0266 | 11300 | 662.3749 |
| 1500 | 959.5179 | 11400 | 659.7837 |
| 1600 | 956.0195 | 11500 | 657.2008 |
| 1700 | 952.5315 | 11600 | 654.626 |
| 1800 | 949.0537 | 11700 | 652.0594 |
| 1900 | 945.5863 | 11800 | 649.501 |
| 2000 | 942.1291 | 11900 | 646.9507 |
| 2100 | 938.6821 | 12000 | 644.4085 |
| 2200 | 935.2454 | 12100 | 641.8744 |
| 2300 | 931.8189 | 12200 | 639.3484 |
| 2400 | 928.4025 | 12300 | 636.8305 |
| 2500 | 924.9963 | 12400 | 634.3206 |
| 2600 | 921.6002 | 12500 | 631.8187 |
| 2700 | 918.2142 | 12600 | 629.3248 |
| 2800 | 914.8383 | 12700 | 626.8388 |
| 2900 | 911.4725 | 12800 | 624.3609 |
| 3000 | 908.1167 | 12900 | 621.8908 |
| 3100 | 904.7709 | 13000 | 619.4287 |
| 3200 | 901.4351 | 13100 | 616.9745 |
| 3300 | 898.1092 | 13200 | 614.5282 |
| 3400 | 894.7933 | 13300 | 612.0897 |
| 3500 | 891.4874 | 13400 | 609.6591 |
| 3600 | 888.1913 | 13500 | 607.2363 |
| 3700 | 884.9051 | 13600 | 604.8212 |
| 3800 | 881.6287 | 13700 | 602.414 |
| 3900 | 878.3622 | 13800 | 600.0146 |
| 4000 | 875.1055 | 13900 | 597.6228 |
| 4100 | 871.8585 | 14000 | 595.2388 |
| 4200 | 868.6214 | 14100 | 592.8626 |
| 4300 | 865.3939 | 14200 | 590.494 |
| 4400 | 862.1762 | 14300 | 588.133 |
| 4500 | 858.9682 | 14400 | 585.7798 |
| 4600 | 855.7699 | 14500 | 583.4341 |
| 4700 | 852.5812 | 14600 | 581.0961 |
| 4800 | 849.4021 | 14700 | 578.7656 |
| 4900 | 846.2326 | 14800 | 576.4427 |
| 5000 | 843.0728 | 14900 | 574.1274 |
| 5100 | 839.9224 | 15000 | 571.8196 |
| 5200 | 836.7817 | 15100 | 569.5194 |
| 5300 | 833.6504 | 15200 | 567.2266 |
| 5400 | 830.5286 | 15300 | 564.9413 |
| 5500 | 827.4163 | 15400 | 562.6635 |
| 5600 | 824.3135 | 15500 | 560.3931 |
| 5700 | 821.2201 | 15600 | 558.1302 |
| 5800 | 818.136 | 15700 | 555.8746 |
| 5900 | 815.0614 | 15800 | 553.6264 |
| 6000 | 811.9962 | 15900 | 551.3856 |
| 6100 | 808.9402 | 16000 | 549.1522 |
| 6200 | 805.8936 | 16100 | 546.9261 |
| 6300 | 802.8563 | 16200 | 544.7073 |
| 6400 | 799.8283 | 16300 | 542.4958 |
| 6500 | 796.8095 | 16400 | 540.2915 |
| 6600 | 793.8 | 16500 | 538.0946 |
| 6700 | 790.7997 | 16600 | 535.9048 |
| 6800 | 787.8085 | 16700 | 533.7223 |
| 6900 | 784.8265 | 16800 | 531.547 |
| 7000 | 781.8537 | 16900 | 529.3789 |
| 7100 | 778.89 | 17000 | 527.2179 |
| 7200 | 775.9354 | 17100 | 525.0641 |
| 7300 | 772.9899 | 17200 | 522.9174 |
| 7400 | 770.0534 | 17300 | 520.7778 |
| 7500 | 767.126 | 17400 | 518.6453 |
| 7600 | 764.2076 | 17500 | 516.5199 |
| 7700 | 761.2982 | 17600 | 514.4016 |
| 7800 | 758.3978 | 17700 | 512.2903 |
| 7900 | 755.5063 | 17800 | 510.186 |
| 8000 | 752.6238 | 17900 | 508.0887 |
| 8100 | 749.7501 | 18000 | 505.9985 |
| 8200 | 746.8854 | 18100 | 503.9151 |
| 8300 | 744.0295 | 18200 | 501.8388 |
| 8400 | 741.1825 | 18300 | 499.7693 |
| 8500 | 738.3443 | 18400 | 497.7068 |
| 8600 | 735.5149 | 18500 | 495.6512 |
| 8700 | 732.6943 | 18600 | 493.6024 |
| 8800 | 729.8825 | 18700 | 491.5606 |
| 8900 | 727.0794 | 18800 | 489.5255 |
| 9000 | 724.285 | 18900 | 487.4973 |
| 9100 | 721.4994 | 19000 | 485.4759 |
| 9200 | 718.7224 | 19100 | 483.4613 |
| 9300 | 715.9541 | 19200 | 481.4535 |
| 9400 | 713.1944 | 19300 | 479.4524 |
| 9500 | 710.4433 | 19400 | 477.4581 |
| 9600 | 707.7009 | 19500 | 475.4705 |
| 9700 | 704.967 | 19600 | 473.4896 |
| 9800 | 702.2417 | 19700 | 471.5153 |
| 9900 | 699.5249 | 19800 | 469.5478 |
| 10000 | 696.8166 | 19900 | 467.5869 |
| 10100 | 694.1168 | 20000 | 465.6326 |
| 10200 | 691.4255 | 21000 | 446.4513 |
| 10300 | 688.7427 | 22000 | 427.9148 |
| 10400 | 686.0683 | 23000 | 410.0066 |
| 10500 | 683.4023 | 24000 | 392.71 |
| 10600 | 680.7447 | 25000 | 376.0092 |
| 10700 | 678.0955 | 26000 | 359.8881 |
| 10800 | 675.4546 | 27000 | 344.3313 |
1 kPa (kiloPascal) equals 0.145 psi.
1 psi = 6.89475729 kPa
1" Hg = 3.386 kPa
| Altitude in Feet | Pressure in kPa | Pressure in PSIA | ||
| 0 | 101.325 | 14.696 | ||
| 5,000 | 84.302 | 12.227 | ||
| 10,000 | 69.678 | 10.106 | ||
| 15,000 | 57.185 | 8.294 | ||
| 20,000 | 46.560 | 6.753 | ||
| 25,000 | 37.600 | 5.454 | ||
| 30,000 | 30.089 | 4.364 | ||
| 35,000 | 23.842 | 3.458 | ||
| 40,000 | 18.754 | 2.720 | ||
| 45,000 | 14.748 | 2.139 | ||
| 50,000 | 11.597 | 1.682 | ||
| 55,000 | 9.122 | 1.323 | ||
| 60,000 | 7.171 | 1.040 | ||
| 65,000 | 5.640 | .818 | ||
| 70,000 | 4.440 | .644 | ||
| 75,000 | 3.496 | .507 | ||
| 80,000 | 2.765 | .401 | ||
| 85,000 | 2.186 | .317 | ||
| 90,000 | 1.731 | .251 | ||
| 95,000 | 1.372 | .199 | ||
| 100,000 | 1.089 | .158 | ||
| 105,000 | .869 | .126 | ||
| 110,000 | .0689 | .100 | ||
| 115,000 | .552 | .080 | ||
| 120,000 | .448 | .065 |