Inches of mercury (inHg) to Atmospheres (atm) Conversion
Inches of mercury
The inch of mercury (inHg) is a unit of pressure equal to the pressure exerted by a column of mercury 1 inch (25.4 mm) high — approximately 3,386.39 Pa or 0.0334 atm. It is used in US aviation for altimeter settings (standard pressure is 29.92 inHg) and in US weather reports for barometric pressure. Pilots set their altimeters in inHg based on local barometric pressure to ensure accurate altitude readings.
Atmospheres
The standard atmosphere (atm) is a unit of pressure defined as exactly 101,325 Pa, representing the approximate mean atmospheric pressure at sea level. It remains in use in chemistry for expressing gas pressures in thermodynamic tables and standard conditions (STP: 0 °C and 1 atm). One atmosphere supports a mercury column of exactly 760 mm — the basis of the mercury barometer invented by Torricelli in 1643. In deep-sea diving, pressure is expressed in atmospheres absolute (ATA).
| Inches of mercury (inHg) | Atmospheres (atm) |
|---|---|
| 0.1 inHg | 0.00334 atm |
| 1 inHg | 0.0334 atm |
| 2 inHg | 0.0668 atm |
| 3 inHg | 0.1003 atm |
| 5 inHg | 0.1671 atm |
| 10 inHg | 0.3342 atm |
| 20 inHg | 0.6684 atm |
| 30 inHg | 1.0026 atm |
| 50 inHg | 1.6711 atm |
| 100 inHg | 3.3421 atm |
| 1000 inHg | 33.4211 atm |
Frequently Asked Questions (FAQ)
How many atmospheres are in 1 inches of mercury?
1 inches of mercury (inHg) is exactly 0.033421 atmospheres (atm).
How do I convert inches of mercury to atmospheres?
Multiply the value in inches of mercury by 0.033421 to get the result in atmospheres. Or use the converter above — type any number and see the result instantly.