Category Speed Pressure Hurricane (mph) .00256V^2 Class 1 95 23.104 PSF Class 2 110 30.976 PSF Class 3 130 43.264 PSF Class 4 155 61.504 PSF Class 5 200 102.4 PSF Tornado F1 72 13.27104 PSF F2 112 32.11264 PSF F3 157 63.10144 PSF F4 206 108.63616 PSF F5 260 173.056 PSF F6 318 258.87744 PSF F7 379 367.72096 PSF Blast 2PSI 70 288 5PSI 163 720 10PSI 294 1440 20PSI 502 2880 50PSI 934 7200 Altitude PSI -1000 15.23 -500 14.96 0 14.696 500 14.43 1000 14.16 2000 14.66 3000 13.17 4000 12.69 5000 12.23 10000 10.1 15000 8.29 20000 6.67