How this calculator works
The conventional factor used here is 133.322387415 Pa per mmHg, calculated as 13595.1 kg/m3 x 9.80665 m/s2 x 0.001 m. NIST tabulates its rounded value as 133.3224 Pa. A standard atmosphere is exactly 101325 Pa. The converter uses the conventional mmHg factor. The torr is exactly 1/760 atmosphere; the two units are extremely close but have different definitions.
Formula
atm = mmHg x 133.322387415 / 101325; mmHg = atm x 101325 / 133.322387415.
Worked example
A pressure of 760 conventional mmHg is about 1.000000142 atm. In reverse, 2 atm is about 1519.999783 mmHg.
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Frequently asked questions
Is 760 mmHg exactly one atmosphere?
That equality is exact for 760 torr. With the conventional NIST mmHg factor used here, the result is very slightly above one atmosphere.
Does mm alone describe pressure?
No. The pressure unit is mmHg, a millimetre-of-mercury convention. A bare millimetre measures length.
Is this a clinical interpretation?
No. It changes pressure units and does not interpret a measurement or suggest treatment.