About

In medical diagnostics and vacuum engineering, the millimeter of mercury (mmHg) remains a standard unit despite the prevalence of SI units. Blood pressure readings, for instance, are universally recorded in mmHg. Converting raw sensor data (typically in Pascals) to this legacy unit requires precise factors to ensure diagnostic accuracy. A deviation of just a few mmHg can alter a hypertension diagnosis.

This tool utilizes the precise definition where one standard atmosphere (101,325 Pa) is exactly 760 mmHg. This yields a conversion factor derived from the density of mercury and standard gravity.

Formulas

The millimeter of mercury is defined by the hydrostatic pressure exerted by a column of mercury 1 mm high at 0°C under standard gravity. The relationship is:

1 mmHg ≈ 133.322387 Pa

To convert from Pascals to mmHg, the formula is:

P_mmHg = P_Pa133.322387

Reference Data

Condition	Pressure (Pa)	Pressure (mmHg)	Clinical/Tech Context
High Vacuum	0.001	~0.0000075	Lab equipment
Low Vacuum	3,300	25	Rough pump limit
Hypotension (Sys)	11,999	90	Low blood pressure
Normal BP (Sys)	15,998	120	Healthy adult
Hypertension Stg 1	18,665	140	High BP threshold
Hypertension Stg 2	21,331	160	Severe High BP
Hypertensive Crisis	24,000	180+	Emergency care
Standard Atm	101,325	760	Sea Level

Frequently Asked Questions

For almost all practical purposes, yes. 1 Torr is defined as 1/760 of a standard atmosphere, while 1 mmHg is defined by the density of mercury. The difference is less than 0.000015%, which is negligible outside of high-precision metrology.

It is a matter of historical continuity and convention. The sphygmomanometer (blood pressure cuff) was originally a mercury column. Medical guidelines and risk thresholds (e.g., 120/80) are firmly established in mmHg.

This tool uses the standard definition derived from 1 atm = 760 mmHg. The divisor used is approximately 133.322387415. Results are rounded to 2 decimal places for readability, which exceeds the precision of standard medical devices.

Yes. Vacuum levels are often measured in mmHg (or Torr). This converter handles the low-pressure ranges required for roughing pumps and HVAC evacuation measurements.