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Precise Conversion

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About

Millimeters of mercury (mmHg) remains the standard unit for blood pressure measurement and aviation altimetry settings. However, raw sensor data or weather reports often arrive in millibars (mbar). This tool allows medical professionals, pilots, and researchers to convert between these units with high precision. Small deviations in mmHg can signify hypertension in a patient or an incorrect altitude setting in an aircraft. The underlying algorithm uses the precise physical definition of mercury density to ensure valid output for diagnostic and safety applications.

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Formulas

The relationship between millibars and mmHg is defined by the density of mercury under standard gravity.

PmmHg Pmbar × 0.75006156

Alternatively, the standard atmosphere definition relates them as:

1013.25 mbar = 760 mmHg

Reference Data

ContextmbarmmHgSignificance
Low Vacuum107.50Lab Equipment
Diastolic (Low)8060.00Hypotension
Diastolic (Normal)10680.00Healthy Heart
Systolic (Normal)160120.00Healthy Heart
Systolic (High)213160.00Hypertension Stage 2
Airline Cabin750562.55~8000ft Altitude
Standard Atmosphere1013.25760.00Sea Level
Hyperbaric Chamber20001500.12Therapy

Frequently Asked Questions

For almost all practical purposes, yes. 1 Torr is defined as 1/760 of a standard atmosphere, while 1 mmHg is the pressure of 1mm of mercury. They differ by less than 0.000015%.
Historically, the first accurate pressure gauges used mercury columns because mercury is dense, allowing the column to be a manageable height (unlike water, which would require a 10-meter tube).
The factor 0.750062 is precise enough for medical and aviation use. Simple approximations using 0.75 result in an error of about 0.008%, which is usually negligible for general use but avoided here for maximum accuracy.
Yes. Antique barometers often read in inches or millimeters of mercury. This tool helps you calibrate them against modern digital weather station reports in mbar.