Convert Millimeter of Mercury to Bar (mmHg → bar)

Converting millimeters of mercury to bars 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 millimeters of mercury

   Start with the number of millimeters of mercury (mmHg) you want to convert.
2. 2
   Multiply by 0.001333

   The conversion factor from mmHg to bar is 0.001333. Multiply your value by this number.
3. 3
   Read the result in bars

   The result is your value in bars (bar).

Multiply the value in millimeters of mercury by 0.001333. For the reverse direction, multiply by 750.06158.

• ✓1 mmHg ≈ 133.32 Pa ≈ 1 Torr.
• ✓760 mmHg = 1 atm.
• ✓Blood-pressure cuffs display mmHg worldwide.

• ✗Confusing mmHg with mmH₂O (different unit, factor of 13.6).
• ✗Mixing mmHg with torr in precise vacuum physics — they differ by one part per million.
• ✗Writing blood pressure in kPa — use mmHg for medical continuity.

What is the Millimeter of Mercury?

The millimeter of mercury equals approximately 133.322 pascals and is the universal medical unit for blood pressure measurements worldwide. Normal blood pressure is around 120/80 mmHg (systolic/diastolic). The unit's origin is the manometer: a column of mercury rises 1 mm for every 133 Pa of pressure difference. Mercury barometers historically measured atmospheric pressure (760 mmHg = 1 atm at sea level). Beyond medicine, mmHg appears in vacuum-system specifications, certain laboratory contexts, and altimeter settings (in inHg in the US, in mmHg or hPa elsewhere). The mmHg relates to the torr (1 mmHg ≈ 1.0000003 torr — essentially identical), the pascal (1 mmHg ≈ 133.3 Pa), the atmosphere (760 mmHg = 1 atm), and inches of mercury (1 inHg = 25.4 mmHg). The unit's persistence in medicine reflects historical inertia and the precision of mercury manometers.

• Blood pressure measurement globally
• Vacuum-system specifications
• Historical scientific texts

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