inch of mercury (inHg)
1 inch of mercury = 3,386.389 pascals
What is inch of mercury?
Inch of mercury (inHg) is a pressure unit representing the pressure exerted by a one-inch column of mercury. It is used in aviation altimetry, barometric pressure readings, and vacuum measurements in the United States.
Notes: Barometric unit
Real-world uses
Inches of mercury are used in US aviation for altimeter settings (standard is 29.92 inHg), weather reporting on American TV broadcasts, and HVAC system vacuum measurements. American barometers are traditionally scaled in inHg.
History
Inches of mercury originate from the mercury barometer invented by Torricelli in 1644. The use of inches (rather than millimetres) reflects the Imperial measurement tradition. US aviation adopted inHg for altimeter settings, while most other countries use hPa.
Common mistakes
Confusing inches of mercury with millimetres of mercury—29.92 inHg = 760 mmHg = 1 atm. Also, assuming the conversion from inHg to psi is simple; 1 inHg ≈ 0.491 psi, not a round number.
When is this conversion used?
Converting between inch of mercury and pascal is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.
How to convert inch of mercury to pascal
To convert inch of mercury to pascal, multiply the value by 3,386.389.
Conversion formula (from base unit)
x * 3386.389
Measurement standards
The pascal (Pa) is the SI derived unit of pressure, defined as one newton per square metre. The World Meteorological Organization mandates the hectopascal (hPa) for atmospheric pressure reporting in aviation and weather services.
Did you know?
The pressure at the bottom of the Mariana Trench, nearly 11 km deep, exceeds 1,086 bar — over a thousand times atmospheric pressure. At this depth, water is compressed by about 5%, making it measurably denser than at the surface.
| inches of mercury | pascals |
|---|---|
| 0.1 | 338.6389 |
| 0.5 | 1,693.1945 |
| 1 | 3,386.389 |
| 2 | 6,772.778 |
| 5 | 16,931.945 |
| 10 | 33,863.89 |
| 25 | 84,659.725 |
| 50 | 169,319.45 |
| 100 | 338,638.9 |
| 250 | 846,597.25 |
| 500 | 1,693,194.5 |
| 1,000 | 3,386,389 |
Common values
| inches of mercury | pascals | |
|---|---|---|
| Car tyre | 64.96595636 inches of mercury | 220,000 pascals |
| Standard atmosphere | 29.9212524 inches of mercury | 101,325 pascals |
| Blood pressure (systolic) | 4.72479683 inches of mercury | 16,000 pascals |
| Deep-sea submersible | 32,482.97818118 inches of mercury | 110,000,000 pascals |
| Bicycle tyre | 183.08587702 inches of mercury | 620,000 pascals |
Full inch of mercury conversion table
| Unit | Value | Factor |
|---|---|---|
| pascal | 1 inHg = 3,386.389 Pa | × 3,386.389 |
| kilopascal | 1 inHg = 3.386389 kPa | × 3.386389 |
| bar | 1 inHg = 0.03386389 bar | × 0.03386389 |
| pound per square inch | 1 inHg = 0.4911542 psi | × 0.4911542 |
| atmosphere | 1 inHg = 0.03342106 atm | × 0.03342106 |
| millibar | 1 inHg = 33.86389 mbar | × 33.86389 |
| hectopascal | 1 inHg = 33.86389 hPa | × 33.86389 |
| torr | 1 inHg = 25.40000632 Torr | × 25.40000632 |
| megapascal | 1 inHg = 0.00338639 MPa | × 0.00338639 |