Convert Bar to Inch of Mercury (bar → inHg)

Converting bars to inches of mercury is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in bars

   Start with the number of bars (bar) you want to convert.
2. 2
   Multiply by 29.52998

   The conversion factor from bar to inHg is 29.52998. Multiply your value by this number.
3. 3
   Read the result in inches of mercury

   The result is your value in inches of mercury (inHg).

Multiply the value in bars by 29.52998. For the reverse direction, multiply by 0.033864.

• ✓1 bar = 100 kPa = 0.987 atm = 14.5 psi.
• ✓Almost 1 atm — convenient approximation.
• ✓Tyre pressures: 2.0–2.5 bar typical car, 6–10 bar truck.

• ✗Assuming 1 bar = 1 atm exactly — 1.3% off.
• ✗Mixing bar with psi — need factor of 14.5.
• ✗Using bar for high-pressure work — switch to MPa.

What is the Bar?

The bar equals exactly 100,000 pascals (100 kPa) and is the everyday pressure unit in European tire pressures, hydraulic systems, and meteorology. The unit was chosen to be approximately equal to atmospheric pressure at sea level (1 bar = 0.987 atm). European cars have tire pressures of about 2.0–2.5 bar (29–36 psi), industrial hydraulic systems operate at 100–700 bar, and wine bottles are pressurized to about 6 bar internally for sparkling wines. Although technically not an SI unit, the bar is widely accepted for use with the SI system. Weather forecasts in some countries use 'millibar' (1 mbar = 1 hPa = 100 Pa) for atmospheric pressure. The bar relates to the pascal (100,000 Pa = 1 bar), the kilopascal (100 kPa = 1 bar), the psi (1 bar ≈ 14.504 psi), the atmosphere (1 atm ≈ 1.013 bar), and the mbar (1,000 mbar = 1 bar). It strikes a practical balance between scientific precision and everyday usefulness.

• European tyre pressure gauges
• Scuba-diving depth pressure
• Hydraulic and pneumatic systems

What is the Inch of Mercury?

The inch of mercury equals exactly 25.4 mmHg (or about 3,386.4 pascals) and is the American aviation standard for altimeter settings and historic barometer readings. Pilots set their altimeters to the local atmospheric pressure in inHg before takeoff and landing — standard 'sea-level pressure' is 29.92 inHg. American weather reports historically used inHg before transitioning to millibars/hPa, and home barometers in the US still display inHg. The unit relates to the mmHg (25.4 mmHg = 1 inHg), the millibar (1 inHg ≈ 33.864 mbar), the kilopascal (1 inHg ≈ 3.386 kPa), and the psi (1 inHg ≈ 0.491 psi). Aviation's continued use of inHg in the United States reflects regulatory tradition rather than scientific advantage; international ATC outside the US uses hectopascals.

• US aviation altimeter QNH settings
• US residential barometers
• US weather forecasts (older)