mmHg to atm Converter

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Convert millimeters of mercury to atmospheres using the exact relation 760 mmHg = 1 atm. Reference values: 120 mmHg ≈ 0.158 atm, 200 mmHg ≈ 0.263 atm, 760 mmHg = 1 atm (sea-level standard). Useful for chemistry gas-law problems, where Torr-precision lab pressures need to be expressed as fractional atmospheres. Browser-local conversion.

Millimeter of mercury (mmHg)
Atmosphere (atm)

Millimeter of mercury (mmHg) → Atmosphere (atm)

Quick reference table

Millimeter of mercury (mmHg)Atmosphere (atm)
60 mmHg0.0789 atm
80 mmHg0.1053 atm
100 mmHg0.1316 atm
120 mmHg0.1579 atm
140 mmHg0.1842 atm
160 mmHg0.2105 atm
200 mmHg0.2632 atm
760 mmHg1 atm

Glossary

Millimeter of mercury (mmHg)

A millimeter of mercury is the pressure exerted by a 1 mm column of mercury at standard gravity, equal to 133.322 Pa. It is the standard unit for blood pressure (120/80 mmHg) and for vacuum-system pressure in laboratory work. The Torr (named after Torricelli) is essentially the same unit — 1 Torr = 1/760 atm differs from 1 mmHg by less than 0.0001 %.

Atmosphere (atm)

A standard atmosphere is defined as exactly 101,325 Pa (= 1.01325 bar = 760 mmHg = 14.696 psi). It represents average atmospheric pressure at sea level under standard conditions. Used in chemistry (gas-law problems), high-altitude aviation references and pressure-vessel ratings. Not the same as the technical atmosphere (at, ≈ 98,066.5 Pa) — that is a separate, rarely used unit.

Metric / SI pressure

In the metric system, pressure is reported in pascals (SI base) or its multiples — kilopascal (kPa, 10³ Pa), megapascal (MPa, 10⁶ Pa) — and the related non-SI unit bar (10⁵ Pa). The millibar/hectopascal (mbar = hPa = 100 Pa) is used in meteorology. All metric units relate by exact powers of ten, so conversions between them are simple shifts of decimal point.

Imperial / US pressure

US engineering and automotive primarily report pressure in pounds per square inch (psi). 1 psi ≈ 6,894.76 Pa, defined as one pound-force per square inch. Standard atmospheric pressure is 14.696 psi. The closely related "psi-gauge" (psi-g) measures pressure above atmospheric, while "psi-absolute" (psi-a) measures total pressure including atmospheric.

Related tools

atm to mmHg
Convert atm to mmHg — 1 atm = 760 mmHg exactly
mmHg to kPa
Convert mmHg to kPa — 1 mmHg ≈ 0.1333 kPa
atm to Bar
Convert atm to bar — 1 atm = 1.01325 bar exactly
Pressure Converter
Convert pressure — Pa, kPa, MPa, bar, mbar, atm, mmHg, psi