Pressure converter: hPa, mmHg, inHg
The ship barometer reads hectopascals, older instruments and books read millimetres of mercury, and American broadcasts read inches of mercury. Type a value in any unit and the converter shows all the others at once.
Quick try:
The hectopascal and the millibar are exactly the same size: a barometer reading 1013 hPa reads 1013 mbar.
Barometric pressure converted
| hPa | mmHg | inHg | psi |
|---|---|---|---|
| 950 | 712.5585 | 28.05348 | 13.77859 |
| 980 | 735.0603 | 28.93938 | 14.2137 |
| 1,000 | 750.0616 | 29.52998 | 14.50377 |
| 1,013.25 | 759.9999 | 29.92126 | 14.69595 |
| 1,020 | 765.0628 | 30.12058 | 14.79385 |
| 1,050 | 787.5647 | 31.00648 | 15.22896 |
Values computed from the exact definitions of the units (NIST SP 811 and the international agreements), rounded to 7 significant digits. The first column is hectopascals.
hPa, mbar and all the rest
The hectopascal and the millibar are the same size (1 hPa = 1 mbar = 100 Pa); meteorology moved to hPa precisely so that the numbers on the charts would not change. Standard pressure, one standard atmosphere, is 1013.25 hPa, that is 760 mmHg or 29.92 inHg.
Psi (pounds per square inch) belongs to engineering rather than weather: compressed air lines, tyres, hydraulics and every gauge that came from the American market. One bar is 14.5 psi, which is a useful number to keep in your head in the engine room.
Frequent questions
How many mmHg is 1 hPa?
About 0.75 mmHg (exactly 1 divided by 1.33322). A rule of thumb: mmHg equals hPa times three quarters.
What is the difference between hPa and mbar?
Nothing but the name. 1 hPa = 1 mbar exactly, so 1013 hPa and 1013 mbar are the same pressure.
What is normal pressure at sea level?
The standard atmosphere is 1013.25 hPa (760 mmHg, 29.92 inHg). Real pressure runs roughly from 950 hPa in a deep low to 1050 hPa in a strong high.
Where is inHg used?
In the United States: weather reports and household barometers, and in aviation the altimeter setting (the standard 29.92 inHg is the same as 1013.25 hPa).