Convert Torr to Millimeter of Mercury (Torr → mmHg)

Converting torr to millimeters 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 torr

   Start with the number of torr (Torr) you want to convert.
2. 2
   Multiply by 1

   The conversion factor from Torr to mmHg is 1. Multiply your value by this number.
3. 3
   Read the result in millimeters of mercury

   The result is your value in millimeters of mercury (mmHg).

Multiply the value in torr by 1. For the reverse direction, multiply by 1.

• ✓1 Torr ≈ 1 mmHg (differ by ~1 ppm — negligible in practice).
• ✓1 atm = 760 Torr exactly.
• ✓Named after Evangelista Torricelli, inventor of the barometer.

• ✗Assuming torr and mmHg are truly identical — they differ by ~10⁻⁷; only matters in metrology.
• ✗Using Torr in everyday context — obscure outside vacuum engineering.
• ✗Mixing Torr and mTorr without specification.

What is the Torr?

The torr equals approximately 1.0000003 mmHg (essentially identical, 133.322 Pa) and is named after Italian physicist Evangelista Torricelli (1608–1647), who invented the mercury barometer. The torr is widely used in vacuum-system specifications, laboratory instruments, and high-vacuum physics. Vacuum levels are categorized: 'low vacuum' is 760 to 1 torr, 'medium vacuum' 1 to 10⁻³ torr, 'high vacuum' below 10⁻³ torr. Mass spectrometers, electron microscopes, and semiconductor manufacturing systems require high vacuum (10⁻⁶ to 10⁻⁹ torr). The torr relates to the mmHg (essentially equal), the pascal (1 torr ≈ 133.3 Pa), the millibar (1 torr ≈ 1.333 mbar), and the atmosphere (760 torr = 1 atm). Modern scientific publications increasingly use the pascal, but the torr remains entrenched in vacuum technology.

• Vacuum-chamber pressure readings
• Semiconductor manufacturing
• Older physics literature

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