Question: what is the difference between in hg and hpa?
Answer: Inches of mercury or inHg is a non-SI unit for pressure. ... Aircraft operating at higher altitudes (above 18,000 feet) set their barometric altimeters to a standard pressure of 29.92 inHg or 1,013.2 hPa (1 hPa = 1 mbar) regardless of the actual sea level pressure, with inches of mercury used in the U.S. and Canada.