Convert Pressure from bar to millimeters of mercury (bar to mmHg)

bar to millimeter of mercury Conversion Formula

Example

Let's convert 5 bar (bar) to millimeter of mercury (mmHg).

Using the formula:

Therefore, 5 bar (bar) is equal to 3750.3187770960531645 millimeter of mercury (mmHg).

How many bar are in one millimeter of mercury? One millimeter of mercury (mmHg) contains 0.00133322 bar (bar) — the inverse of the factor above. Multiplying by 750.0637554192106329 takes you from bar to millimeters of mercury; multiplying by 0.00133322 brings you back.

Put in words: one bar equals 750.0637554192106329 millimeters of mercury, so the bar is the larger unit of this pair. Converting between them never changes the amount of pressure being measured — only the size of the unit you count it in.

What is a bar (bar)?

The bar is a metric unit of pressure.

It is defined as exactly 100 kilopascals (kPa), or 100,000 Pascals (Pa).

Although it is not an official part of the International System of Units (SI), it is widely accepted for use with the SI. The bar is a popular unit for measuring pressure because it is very close to the average atmospheric pressure on Earth at sea level.

Origin of the Bar

The term "bar" comes from the Greek word βάρος (baros), which means "weight."

The unit was introduced by British meteorologist William Napier Shaw in 1909. It is still widely used in meteorology, oceanography, and engineering.

Bar vs. Standard Atmosphere (atm)

A common point of confusion is the difference between a bar and a standard atmosphere (atm).

While they are very close in value, they are not the same:

• 1 bar = 100,000 Pascals (Pa)
• 1 atmosphere (atm) = 101,325 Pascals (Pa)

This means 1 bar is approximately equal to 0.987 atm. Because it's so close to atmospheric pressure and is a round number (100 kPa), the bar is a very convenient unit for many applications.

Common Applications of the Bar

The bar is a versatile unit used to measure pressure in many industrial and everyday contexts.

Common examples include:

• Automotive: Measuring tire pressure (often listed on a car's door jamb alongside PSI).
• Scuba Diving: Expressing the amount of air pressure inside diving tanks.
• Weather: Used by meteorologists for weather forecasting and reading atmospheric pressure.
• Plumbing & Pumps: Measuring water pressure in pipes and pump systems.
• Industrial: Measuring air pressure in pneumatic equipment and gas pressure in cylinders for welding.

What Is a Millimeter of Mercury (mmHg)?

A millimeter of mercury (mmHg) is a manometric unit of pressure.

It was historically defined as the pressure generated by a column of mercury exactly one millimeter high.

Today, it is most famous as the unit used in medicine for measuring blood pressure. It is also commonly used in meteorology, aviation, and physics to measure atmospheric pressure or vacuum pressure.

The Origin of the mmHg Unit

The mmHg unit originates from the invention of the barometer by Evangelista Torricelli in 1643.

Torricelli's device measured atmospheric pressure by seeing how high it could support a column of mercury in a tube.

Standard atmospheric pressure was found to support a column approximately 760 mm high, which established 760 mmHg as a standard reference point.

Common Applications of mmHg

The most well-known application of mmHg is in medicine.

• Blood Pressure: Readings are given as two numbers: systolic pressure (when the heart beats) over diastolic pressure (when the heart rests), such as 120/80 mmHg. This is a critical vital sign for human health.

• Meteorology: Used for reporting barometric (atmospheric) pressure, which helps in weather forecasting.

• Physics & Engineering: Used for measuring vacuum pressures and other low-pressure systems where precision is needed.

How to Convert mmHg to Other Pressure Units

While mmHg is common, other pressure units are standard in different fields. Here are the most common conversions:

• 1 mmHg = 133.322 pascals (Pa)
• 1 mmHg = 0.133322 kilopascals (kPa)
• 760 mmHg = 1 standard atmosphere (atm)

bar to millimeter of mercury Conversion Table

Here are some quick reference conversions from bar (bar) to millimeter of mercury (mmHg):