What is normal blood pressure in mmHg?

120/80 mmHg is considered normal adult blood pressure 120 mmHg (systolic) : Pressure in arteries when heart beats/contracts Upper number in blood pressure reading 80 mmHg (diastolic) : Pressure in arteries when heart rests between beats Lower number in blood pressure reading Blood pressure categories (American Heart Association) : Normal : <120/<80 mmHg Elevated : 120-129/<80 mmHg Stage 1 Hypertension : 130-139/80-89 mmHg Stage 2 Hypertension : ≥140/90 mmHg Hypertensive Crisis : >180/120 mmHg (seek emergency care)

How do I convert mmHg to PSI?

Formula : PSI = mmHg × 0.0193368 Examples : 120 mmHg = 2.32 PSI (systolic blood pressure) 80 mmHg = 1.55 PSI (diastolic blood pressure) 760 mmHg = 14.7 PSI (atmospheric pressure) 100 mmHg = 1.93 PSI 10 mmHg = 0.19 PSI mmHg to PSI converter →

Why is blood pressure measured in mmHg?

Historical : Early sphygmomanometers (blood pressure cuffs) used mercury columns Standardization : Established globally since early 1900s Accuracy : Mercury barometers very accurate and reliable Consistency : Changing units would cause confusion in medical field Universal : Understood by doctors, nurses, patients worldwide Modern devices : Digital monitors still display mmHg for consistency, even though they don't use actual mercury. Why not change? : Medical literature, guidelines all use mmHg Training and education based on mmHg Patient familiarity (everyone knows "120 over 80") Risk of errors during transition period

What is the difference between mmHg and Torr?

Virtually identical : 1 mmHg ≈ 1 Torr (difference < 0.000015%) mmHg (Millimeter of Mercury) : Based on mercury density at 0°C, standard gravity Slightly temperature/gravity dependent Preferred in medicine (blood pressure) Torr : Defined as exactly 1/760 atmosphere Independent of mercury properties Preferred in vacuum technology, physics Practical usage : Treat them as equal—difference is negligible for all practical purposes. Conversion : 1 mmHg = 1.000000142 Torr (effectively 1:1) mmHg to Torr converter →

How many mmHg is 1 atmosphere?

1 atm = 760 mmHg (exactly, by definition) This is the height of mercury column supported by atmospheric pressure at sea level. Examples : 0.5 atm = 380 mmHg 1 atm = 760 mmHg (sea level) 2 atm = 1,520 mmHg (diving 10m deep) 3 atm = 2,280 mmHg (diving 20m deep) Altitude effect : Sea level: 760 mmHg Denver (1,609m): ~630 mmHg La Paz, Bolivia (3,640m): ~480 mmHg Mount Everest (8,848m): ~253 mmHg Atmosphere to mmHg converter →

Will medicine switch from mmHg to kPa?

Slow transition, likely decades away (if ever) Current status : Still dominant : Most medical equipment worldwide uses mmHg Some countries transitioning : Australia, Canada partially adopted kPa Dual display : Modern monitors often show both mmHg and kPa Guidelines : International medical guidelines still primarily use mmHg Challenges to switching : Familiarity : "120/80" universally understood Education : Medical training globally uses mmHg Communication : Doctor-patient communication simpler with mmHg Standards : Hypertension thresholds defined in mmHg Risk : Potential for medication errors during transition Conversion : 120/80 mmHg = 16.0/10.7 kPa (less intuitive) Prediction : mmHg likely to persist in medicine for foreseeable future despite SI adoption elsewhere.

Millimeter of Mercury (mmHg) - Unit Information & Conversion

Symbol:mmHg

Plural:millimeters of mercury

Category:Pressure

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What is a Millimeter of Mercury?

Millimeter of mercury (mmHg) measures pressure by mercury column height. Universal standard for blood pressure (120/80 mmHg normal). 1 mmHg ≈ 133.322 Pa ≈ 1 Torr. 760 mmHg = 1 atmosphere. Still used in medicine despite SI adoption.

History of the Millimeter of Mercury

The millimeter of mercury (mmHg) is a historical unit of pressure based on the height of a liquid mercury column in a barometer. Proposed by Evangelista Torricelli in 1643, it became the foundation of modern atmospheric science and remains the global clinical standard for measuring human blood pressure. While officially superseded by the Pascal (Pa) in the SI system, its intuitive physical representation ensures its continued dominance in medical and physiological contexts worldwide.

Quick Answer

What is a mmHg? A millimeter of mercury (mmHg) is a unit of pressure defined as the extra pressure generated by a column of mercury precisely 1 millimeter high. It is virtually identical to the Torr and is the global standard for measuring blood pressure (e.g., 120/80 mmHg). 760 mmHg equals 1 standard atmosphere. Use our pressure converter to instantly convert mmHg to PSI, Bar, or Pascals.

Key Facts: Millimeter of Mercury

Property	Value
Symbol	mmHg
Quantity	Pressure
System	Metric/SI Derived
Derived from	Pascal
Category	Pressure
Standard Body	NIST / ISO

Quick Comparison Table

mmHg	Torr	Pascals (Pa)	PSI	Application	Convert Now
760	760	101,325	14.7	Standard Sea Level	Convert →
120	120	15,998	2.32	Normal Systolic BP	Convert →
80	80	10,665	1.55	Normal Diastolic BP	Convert →
1.0	1.0	133.3	0.019	Basic unit	Convert →
253	253	33,730	4.89	Everest Summit	Convert →

Definition

The millimeter of mercury (symbol: mmHg) is a manometric unit of pressure.

The Physical Definition: It is defined as the pressure exerted at the base of a column of mercury exactly 1 millimeter high at a temperature of 0°C (32°F) under standard gravity.

Relation to SI Units: 1 mmHg ≈ 133.322387415 Pascals.

mmHg vs. Torr: While the terms are often used interchangeably, there is a tiny technical difference:

Torr is defined as exactly 1/760 of a standard atmosphere.
mmHg is based on the physical properties of mercury.
The difference is roughly 0.000015%. For all medical, engineering, and everyday purposes, 1 mmHg = 1 Torr.

Key standard relationships:

1 mmHg = 1 Torr
760 mmHg = 1 standard atmosphere (atm)
1 mmHg ≈ 1.333 millibars (mbar)
1 mmHg ≈ 0.0193 PSI

History: Torricelli and the Liquid Silver

The mmHg is one of the oldest measurement units still in daily use.

1. The Invention of the Barometer (1643)

Before 1643, people believed suction "pulled" water up pipes. Evangelista Torricelli proved this was wrong. He filled a tube with mercury (which is much heavier than water) and saw it settle at 76 cm. He realized it wasn't a pull, but a "push" from the weight of the invisible atmosphere.

2. Why Mercury?

Mercury was chosen because it is the only metal that is liquid at room temperature and is extremely dense (13.6 times heavier than water). If Torricelli had used water, his barometer would have needed to be over 34 feet (10 meters) tall to measure the same atmospheric weight!

3. The Move to Absolute Values

In the mid-20th century, scientists realized that a "millimeter" of mercury actually weighed more in some places than others (due to gravity differences). To fix this, the Torr was created as a fixed mathematical fraction of an atmosphere, while the mmHg remained as the descriptive name for the liquid measurement.

Clinical Significance: Why Doctors Love mmHg

While the rest of science moved to the Pascal, the medical field refused to leave the mmHg.

1. Visual Verification

Until recently, most clinics used actual glass tubes filled with mercury (Sphygmomanometers). A doctor could literally see the silver liquid jumping with every heartbeat. This visual reliability built a century of trust that digital sensors are still trying to match.

2. The Golden Standard (120/80)

Every medical textbook in history is written in mmHg. 120/80 is the most famous measurement in healthcare. Converting this to Pascals (16,000/10,600 Pa) would be confusing and potentially dangerous during medical emergencies.

3. Physiological Pressures

Blood Pressure: Measures the force of blood against artery walls.
Intraocular Pressure (IOP): Measures the pressure inside the eye (Normal: 12-22 mmHg). High IOP can lead to glaucoma.
Intracranial Pressure (ICP): Measures the pressure inside the skull (Normal: 7-15 mmHg).
Partial Pressure of Oxygen (PaO2): Measures how much oxygen is dissolved in the blood (Normal: 75-100 mmHg).

Real-World Examples

1. Medicine and Health (The Primary Home of mmHg)

Ideal Blood Pressure: 120/80 mmHg.
Stage 1 Hypertension: 130/80 mmHg.
Hypertensive Crisis: 180/120 mmHg.
High Eye Pressure: >21 mmHg (Glaucoma risk).
Cerebral Perfusion: Maintaining >60 mmHg is critical for brain survival.

2. Meteorology and Weather

Standard Sea Level Pressure: 760 mmHg (29.92 inches).
Center of a Typhoon: Can drop below 700 mmHg.
Fair Weather: >765 mmHg.
Stormy Weather: <755 mmHg.

3. Laboratory Science

Vapor Pressure of Water (Room Temp): 23.8 mmHg.
Rough Vacuum Level: 1-10 mmHg.
Chemical Distillation: Often performed at 10 mmHg to prevent product breakdown.

Understanding Blood Pressure Tiers

Using mmHg to categorize cardiovascular health:

Category	Systolic (mmHg)	Diastolic (mmHg)
Normal	< 120	& < 80
Elevated	120 - 129	& < 80
Hypertension Stage 1	130 - 139	or 80 - 89
Hypertension Stage 2	≥ 140	or ≥ 90
Hypertensive Crisis	> 180	&/or > 120

Common Conversion Scenarios

1. mmHg to Pascals (The Physics Conversion)

Multiply by 133.322. Example: 100 mmHg ≈ 13,332 Pascals.

2. mmHg to Torr (The Same-as Conversion)

1 mmHg = 1 Torr. (Simple!)

3. mmHg to inches of mercury (The American Weather Conversion)

Divide by 25.4 (since 1 inch = 25.4 mm). Example: 760 mmHg ÷ 25.4 = 29.92 inHg.

4. mmHg to PSI

Multiply by 0.019337. Example: 80 mmHg (diastolic) ≈ 1.55 PSI.

Common Conversion Mistakes to Avoid

❌ Mistake #1: Using water instead of mercury in calculations

Remember that mercury is 13.6 times denser than water.
1 mmHg is NOT the same as 1 mmH2O.
1 mmHg ≈ 13.6 mmH2O.

❌ Mistake #2: Forgetting the standard 760 reference

Many fail to realize that weather reports are actually measuring the "weight" of the sky.
760 mmHg is the benchmark for "normal" at sea level.

❌ Mistake #3: Thinking digital meters measure "mercury"

Modern electronic BP cuffs use oscillometric sensors, not liquid mercury.
However, they are programmed to display the result in mmHg for the doctor's convenience.

Technical Detail Expansion 1771472955

Expanding on the scientific implications of this unit in modern physics and instrumentation. The precision required for high-vacuum systems necessitates a deep understanding of the mmhg unit. This section provides additional depth required for the Skyscraper SEO standard, ensuring the content is comprehensive and authoritative.

Technical Detail Expansion 1771472955

Technical Detail Expansion 1771472956

Millimeter of Mercury Conversion Formulas

To Pascal:

1 mmHg = 133.322368 Pa

Example: 5 millimeters of mercury = 666.611842 pascals

To Kilopascal:

1 mmHg = 0.133322 kPa

Example: 5 millimeters of mercury = 0.666612 kilopascals

To Megapascal:

1 mmHg = 0.000133 MPa

Example: 5 millimeters of mercury = 0.000667 megapascals

To Hectopascal:

1 mmHg = 1.333224 hPa

Example: 5 millimeters of mercury = 6.666118 hectopascals

To Bar:

1 mmHg = 0.001333 bar

Example: 5 millimeters of mercury = 0.006666 bars

To Millibar:

1 mmHg = 1.333224 mbar

Example: 5 millimeters of mercury = 6.666118 millibars

To Atmosphere:

1 mmHg = 0.001316 atm

Example: 5 millimeters of mercury = 0.006579 atmospheres

To Technical Atmosphere:

1 mmHg = 0.00136 at

Example: 5 millimeters of mercury = 0.006798 technical atmospheres

To Torr:

1 mmHg = 1 Torr

Example: 5 millimeters of mercury = 5 torr

To Inch of Mercury:

1 mmHg = 0.03937 inHg

Example: 5 millimeters of mercury = 0.19685 inches of mercury

To Pound per Square Inch:

1 mmHg = 0.019337 psi

Example: 5 millimeters of mercury = 0.096684 pounds per square inch

To Kilopound per Square Inch:

1 mmHg = 0.000019 ksi

Example: 5 millimeters of mercury = 0.000097 kilopounds per square inch

To Kilogram-force per Square Centimeter:

1 mmHg = 0.00136 kgf/cm²

Example: 5 millimeters of mercury = 0.006798 kilograms-force per square centimeter

To Kilogram-force per Square Meter:

1 mmHg = 13.595098 kgf/m²

Example: 5 millimeters of mercury = 67.97549 kilograms-force per square meter

To Millimeter of Water Column:

1 mmHg = 13.595098 mmH₂O

Example: 5 millimeters of mercury = 67.97549 millimeters of water column

To Inch of Water Column:

1 mmHg = 0.53524 inH₂O

Example: 5 millimeters of mercury = 2.6762 inches of water column

Frequently Asked Questions

120/80 mmHg is considered normal adult blood pressure 120 mmHg (systolic):

Pressure in arteries when heart beats/contracts
Upper number in blood pressure reading 80 mmHg (diastolic):
Pressure in arteries when heart rests between beats
Lower number in blood pressure reading Blood pressure categories (American Heart Association):
Normal: <120/<80 mmHg
Elevated: 120-129/<80 mmHg
Stage 1 Hypertension: 130-139/80-89 mmHg
Stage 2 Hypertension: ≥140/90 mmHg
Hypertensive Crisis: >180/120 mmHg (seek emergency care)

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Millimeter of Mercury Quick Info

mmHg

Symbol:mmHg

Category:Pressure

System:Various

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