How to use: Calculate atmospheric pressure adjusted for altitude and temperature. Enter Sea Level Pressure (standard: 29.92 inHg or 1013.25 hPa) and select unit. Enter Altitude (elevation above sea level) in feet or meters. Enter Temperature and select unit. Results show adjusted barometric pressure at your location. Pressure decreases ~1 inHg per 1,000 ft elevation gain. Pressure patterns: Rising pressure = improving weather/clear skies, Falling pressure = approaching storm/precipitation, Steady pressure = stable conditions. Typical range: 28-31 inHg (948-1050 hPa). Used for: weather forecasting, altimeter calibration, aviation flight planning, and barometric trend analysis. Low pressure systems bring clouds/rain, high pressure brings clear skies.