Convert Pressure from millimeters of mercury to kilopascals (mmHg to kPa)

Millimeter of Mercury to Kilopascal Conversion Formula

To convert a pressure from millimeters of mercury (mmHg) to kilopascals (kPa), multiply by 0.13332.

• kPa = mmHg × 0.13332

The conventional millimeter of mercury is defined as 133.322 Pa, so dividing by 1,000 gives the kPa factor. Two anchors cover most uses: 760 mmHg = 101.32 kPa (one atmosphere), and 7.5 mmHg ≈ 1 kPa for quick mental division.

Step-by-Step Example

A blood-pressure reading of 120 mmHg (systolic) needs to be recorded in SI units for a research protocol:

1. Take the pressure: 120 mmHg
2. Multiply by 0.13332: 120 × 0.13332 = 16.0 kPa

The familiar "120 over 80" therefore becomes "16.0 over 10.7" in kilopascals. For the reverse conversion multiply kPa by 7.5006.

Quick Reference Table

A Conversion Medicine Can't Avoid

mmHg survives almost entirely because of medicine: blood pressure, intraocular pressure, ventilator settings, blood-gas partial pressures (PaO₂, PaCO₂) and central venous pressure are all traditionally quoted in millimeters of mercury. But the scientific literature, SI-based hospital systems in some countries, and physiology calculations (gas laws, alveolar equations) want kPa — several European countries report blood gases in kPa as standard, so clinicians moving between systems convert constantly: a PaCO₂ of 40 mmHg is 5.3 kPa. Outside medicine the pairing appears in vacuum measurement and in older engineering texts. The practical habit is to memorize one clean crossover in your own field — 7.5 mmHg per kPa, or "normal PaO₂ ≈ 100 mmHg ≈ 13.3 kPa" — and let it flag any converted value that lands an order of magnitude off.

How many millimeters of mercury are in one kilopascal? One kilopascal (kPa) contains 7.500637554192106329 millimeters of mercury (mmHg) — the inverse of the factor above. Multiplying by 0.133322 takes you from millimeters of mercury to kilopascals; multiplying by 7.500637554192106329 brings you back.

Put in words: one millimeter of mercury equals 0.133322 kilopascals, so the millimeter of mercury is the smaller 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 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)

What is a kilopascal (kPa)?

A kilopascal (kPa) is a metric unit of pressure that equals 1,000 pascals.

It is one of the most common units for measuring pressure worldwide, used in both scientific and everyday applications.

The Kilopascal (kPa) Explained

The base unit, the pascal (Pa), is named after the French polymath Blaise Pascal.

As part of the metric system (also known as the SI system), the kilopascal is widely used in scientific, engineering, and industrial fields due to its standardization and ease of calculation.

Common Applications of Kilopascals (kPa)

The kPa unit is used to measure pressure in many everyday and technical contexts. Common examples include:

• Tire Pressure: A common measurement for vehicle tire pressure in many countries outside the US.
• Weather Forecasting: Used for reporting atmospheric pressure.
• HVAC Systems: Essential for measuring differential pressure in heating, ventilation, and air conditioning systems.
• Medical: Frequently used for measuring blood pressure.
• Manufacturing: Critical for monitoring pressure in various industrial processes.

Kilopascal Conversions (kPa to PSI and Bar)

For practical use, it's essential to understand how kPa converts to other common pressure units.

• kPa to PSI: 1 kPa is approximately 0.145 PSI (Pounds per Square Inch). PSI is the standard pressure unit used in the United States.
• kPa to Bar: 100 kPa is exactly equal to 1 bar. The bar is another metric unit frequently used for atmospheric and water pressure.

millimeter of mercury to kilopascal Conversion Table

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

This conversion in other languages

Engineering datasheets across Europe write millimeter of mercury to kilopascal several different ways. The calculation is the same in every one of them.