mmHg to atm Conversion Calculator — Millimetres of Mercury to All Pressure Units
Convert millimetres of mercury (mmHg) to standard atmospheres (atm), pascals, kilopascals, bar, psi, inHg, Torr and millibar — or enter any of those units to get mmHg. The default 760 mmHg equals exactly 1 standard atmosphere.
From unit
760 mmHg = 1 atm = 101,325 Pa = 1.01325 bar = 14.696 psi
- 1
Convert to pascals
760 × 133.322387 = 101,325.01411 mmHg = 133.322387 Pa - 2
Convert Pa to mmHg
101,325.0141 ÷ 133.322387 = 760
How does this calculator work?
760 mmHg = 1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar = 14.696 psi = 29.921 inHg = 760 Torr = 1013.25 mbar. Enter any pressure in mmHg (or convert from any unit) to get all equivalents instantly. mmHg remains the clinical standard for blood pressure worldwide.
Formula
How this is calculated
A millimetre of mercury (mmHg) is a pressure unit that originally referred to the pressure exerted by a 1 mm column of mercury under standard conditions (0 °C, standard gravity). It is still the universal unit for blood pressure measurement (a "normal" blood pressure of 120/80 is quoted in mmHg) and for many medical and meteorological applications.
All conversions here use the pascal (Pa) as the intermediate base unit. One mmHg equals 133.322387 Pa, derived from mercury's density at 0 °C (13,595.1 kg/m³) and standard gravity (9.80665 m/s²). The standard atmosphere is defined as exactly 101,325 Pa, which means 1 atm = 101,325 / 133.322387 ≈ 760 mmHg — this historic "760 mmHg per atm" relationship is why mmHg survives in clinical and meteorological practice.
Note: the Torr is defined as exactly 1/760 atm ≈ 133.322368 Pa, which is very close to but not identical to 1 mmHg (difference of about 0.000015 Pa). For most practical purposes they are interchangeable, but they differ by definition. These conversions treat them separately for precision. All values are absolute pressures; for gauge pressure (e.g. blood-pressure cuff), add local atmospheric pressure (~760 mmHg) to convert to absolute.
Frequently asked questions
The sphygmomanometer (blood pressure cuff) was invented in the 19th century using a mercury column to measure pressure. Even though modern devices are electronic, the mmHg unit was retained for continuity in clinical reporting. 1 mmHg is approximately 133.3 Pa; a typical systolic pressure of 120 mmHg is about 0.158 atm above ambient.
Nearly but not exactly. 1 Torr is defined as exactly 1/760 standard atmosphere ≈ 133.3224 Pa, while 1 mmHg is defined from mercury's physical properties ≈ 133.3224 Pa — the values differ by less than 0.000015 Pa, making them identical for all practical purposes. This calculator shows both separately for precision.
1 bar = 100,000 Pa. Since 1 mmHg = 133.322387 Pa, 1 bar = 100,000 / 133.322387 ≈ 750.06 mmHg. Standard atmospheric pressure (1 atm = 760 mmHg) is slightly above 1 bar (1 atm = 1.01325 bar).
Also known as
TG we-Calculate Editorial Team. (2026). mmHg to atm Conversion Calculator — Millimetres of Mercury to All Pressure Units [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/mmhg-to-atm-conversion-calculator
TG we-Calculate Editorial Team. "mmHg to atm Conversion Calculator — Millimetres of Mercury to All Pressure Units." TG we-Calculate. 2026. https://we-calculate.com/calculator/mmhg-to-atm-conversion-calculator.
TG we-Calculate Editorial Team, "mmHg to atm Conversion Calculator — Millimetres of Mercury to All Pressure Units," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/mmhg-to-atm-conversion-calculator
@misc{wecalculate_mmhg_to_atm_conversion_calculator, title = {mmHg to atm Conversion Calculator — Millimetres of Mercury to All Pressure Units}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/mmhg-to-atm-conversion-calculator}}, year = {2026}, note = {TG we-Calculate} }
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