Standard atmosphere: 1 atm = 1013.25 hPa = 760 mmHg = 29.9213 inHg = 14.696 psi = 101.325 kPa.
Weather context: Normal range is roughly 980–1050 hPa. Below 1000 hPa often indicates low pressure (storms), above 1025 hPa indicates high pressure (fair weather).