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mmHg to Torr Converter
↔ Convert torr to mmHg instead

Common Conversions

mmHg torr
1 1
10 10
23.8 23.8
50 50
100 100
200 200
400 400
500 500
600 600
760 760
800 800
1000 1000

Why this conversion matters in chemistry

Pulmonary gas-exchange calculations cross this identity routinely. Clinical PCO₂ at 40 mmHg arterial pressure is 40 torr in the underlying physical-chemistry framework — the two units are interchangeable in any practical calculation. Both descend from mercury-column measurements: mmHg from the literal column height, torr defined as exactly 1/760 of a standard atmosphere. The two definitions match to about 0.000015%, well below the precision of any practical measurement. The identity is the everyday type cast at the boundary between clinical and physical-chemistry literature.

Formula

torr = mmHg × 1 (numerically identical)

Worked Examples

760 mmHg = 760 torr

Standard atmospheric pressure at sea level.

23.8 mmHg = 23.8 torr

Vapor pressure of water at 25 °C — the value behind humid-air calculations.

1 mmHg = 1 torr

The base unit relationship — practically identical.

400 mmHg = 400 torr

About a typical vacuum-distillation operating pressure.

Frequently Asked Questions

Are mmHg and torr the same?
For all practical chemistry purposes, yes. 1 mmHg = 1 torr to about 0.000015% — well below the precision of any pressure-measurement instrument. The torr is defined as exactly 1/760 of a standard atmosphere.
Why do both units exist?
mmHg originated as the literal height of a mercury column on a manometer; the torr was named after Evangelista Torricelli and defined to closely match mmHg while being formally tied to the standard atmosphere. The two converged historically but kept their separate names.
When should I use mmHg versus torr?
Chemistry and physics literature defaults to torr. Medical practice (blood pressure, partial pressures) defaults to mmHg. In any quantitative calculation the two are interchangeable.
What's standard atmospheric pressure in mmHg?
Exactly 760 mmHg, equivalently 760 torr, equivalently 101.325 kPa or 1 atm. The chain links the historical mercury-column scales to the modern SI form.