Team Physics -
Created by: Team Physics -, Last Updated: April 25, 2024


Torr is a unit of pressure based on an absolute scale, defined as 1/760 of a standard atmosphere, approximately equivalent to the pressure exerted by a millimeter of mercury (mmHg). In other units, one Torr is roughly equal to 133.322 pascals (Pa), 0.00133322 Bars, or 0.0193368 pounds per square inch (psi). It is commonly used in vacuum physics and other applications requiring fine measurements of pressure. Named after Evangelista Torricelli, the inventor of the barometer, the Torr helps bridge practical laboratory work with the theoretical calculations in physics, maintaining relevance in both scientific and industrial settings.

What is Torr?

The Torr is a unit of pressure named after Evangelista Torricelli, the inventor of the barometer. It is defined as exactly 1/760 of a standard atmosphere, equivalent to the pressure exerted by a millimeter of mercury (mmHg). Torr is commonly used in fields requiring precise measurement of low pressures, such as in vacuum systems and meteorology.

Torr Formula

Torr = Atmospheres×760

This formula simply multiplies the pressure in atmospheres by 760 to convert it to Torr. This is because 1 atm equals 760 Torr by definition. Thus, if you know the pressure in atmospheres, you can easily calculate the pressure in Torr using this multiplication factor.

Practical Example for the Torr

Vacuum Packaging Process

In the food industry, vacuum packaging is a common method to extend the shelf life of products by removing air from the package, which helps to inhibit the growth of bacteria and other spoilage organisms. The effectiveness of the vacuum process is often measured in Torr to ensure that the pressure is low enough to achieve desired preservation results.

Scenario: A food processing plant needs to determine the effectiveness of their vacuum packaging machine. The machine specifications state that it should achieve a vacuum level of 50 Torr to ensure optimal food preservation.

Application: The technicians use a vacuum gauge that reads in Torr to monitor the vacuum level during the packaging process. After starting the machine, they observe that the gauge stabilizes at 50 Torr, indicating that the internal pressure of the packaging is sufficiently low to retard spoilage effectively.

In this scenario, using Torr as the measurement unit allows precise control over the packaging environment, directly influencing product quality and safety. This example demonstrates how Torr is practically applied in industry to manage and optimize processes that depend on specific pressure conditions.

Gas Pressure Torr

Gas pressure measured in Torr provides a practical way to understand pressure systems, particularly in contexts where precise measurements of low pressure are crucial, such as in scientific laboratories or industrial processes. Here’s an explanation with a real-world example:

Example of Gas Pressure Torr

Laboratory Vacuum Chambers

In a physics laboratory, researchers are conducting experiments in a vacuum chamber where precise control of the environment is essential. These experiments might include studying the behavior of gases at low pressures or observing chemical reactions that occur only in near-vacuum conditions.

The laboratory vacuum chamber is equipped with a pressure gauge that measures in Torr to monitor and adjust the gas pressure accurately. For a particular experiment, researchers aim to reduce the internal pressure of the chamber to 10 Torr to simulate space-like conditions.

Initial Setup: The chamber starts at atmospheric pressure, which is approximately 760 Torr.
Vacuum Pump Activation: The researchers activate the vacuum pump, and the pressure begins to drop. They monitor the gauge closely.
Reaching Target Pressure: After a period, the gauge reads 10 Torr, indicating that most of the air has been evacuated and the desired vacuum level has been achieved.
Conducting Experiments: With the chamber stabilized at 10 Torr, the researchers proceed with their experiments, able to replicate conditions that are critical for their research.

High Vacuum Torr

High vacuum conditions are typically measured in Torr, which is crucial for many scientific and industrial applications where extremely low pressures are required. Here’s how high vacuum is typically used, with a specific example to illustrate:

Example of Gas Pressure Torr

Semiconductor Manufacturing

Scenario: In the production of semiconductors, maintaining a high vacuum environment is essential. This controlled environment prevents contamination and allows for the precise deposition of materials onto silicon wafers.

Application: During the process of physical vapor deposition (PVD), a high vacuum is needed to ensure that the vaporized metals can be deposited thinly and evenly without interference from air molecules.

  • Vacuum Creation: The manufacturing equipment includes a vacuum chamber that is pumped down to a high vacuum level, often below 10^-6 Torr. This extreme low pressure ensures that there are very few gas molecules inside the chamber.
  • Monitoring Pressure: Specialized vacuum gauges capable of detecting very low pressures are used to monitor and maintain the vacuum within the specified range. The pressure needs to be kept consistently low to prevent any inconsistencies in the thin films being deposited.
  • Deposition Process: With the chamber at high vacuum, metals like aluminum or copper are vaporized in the chamber. The absence of air molecules ensures that the vaporized metal travels unimpeded to the substrate where it condenses, forming a uniform film.
  • Quality Assurance: Maintaining a high vacuum is critical for the quality of the semiconductor devices. Any deviation in vacuum levels can lead to defects in the semiconductor layers, impacting the performance of the final product.

SI multiples of Torr

SI PrefixSymbolMultiplier to PascalEquivalent in Torr
Kilo-kPa10³ Pa1 kPa = 7.50062 Torr
Mega-MPa10⁶ Pa1 MPa = 7500.62 Torr
Giga-GPa10⁹ Pa1 GPa = 7,500,620 Torr
Milli-mPa10−3 Pa1 mPa = 0.00750062 Torr
Micro-µPa10⁻³ Pa1 µPa = 0.00000750062 Torr
Nano-nPa10⁻⁹ Pa1 nPa = 0.00000000750062 Torr
Pico-pPa10⁻¹² Pa1 pPa = 0.00000000000750062 Torr
Femto-fPa10⁻¹⁵ Pa1 fPa = 0.00000000000000750062 Torr

Conversion of Torr into other Units

Units of Torr
To UnitConversion FactorConversion from 10 Torr
Torr to Pascals (Pa)1 Torr = 133.322 Pa10 Torr = 1,333.22 Pa
Torr to Kilopascals (kPa)1 Torr = 0.133322 kPa10 Torr = 1.33322 kPa
Torr to Megapascals (MPa)1 Torr = 0.000133322 MPa10 Torr = 0.00133322 MPa
Torr to Bars1 Torr = 0.00133322 bar10 Torr = 0.0133322 bar
Torr to Millibars (mbar)1 Torr = 1.33322 mbar10 Torr = 13.3322 mbar
Torr to Pounds per Square Inch (psi)1 Torr = 0.0193368 psi10 Torr = 0.193368 psi
Torr to Standard Atmospheres (atm)1 Torr = 0.00131579 atm10 Torr = 0.0131579 atm
Torr to Inches of Mercury (inHg)1 Torr = 0.0393701 inHg10 Torr = 0.393701 inHg
Torr to Inches of Water (inH2O)1 Torr = 0.53524 inH2O10 Torr = 5.3524 inH2O
Torr to Atmospheres (Technical)1 Torr = 0.00135951 at10 Torr = 0.0135951 at
Torr to Kilograms per Square Centimeter (kg/cm²)1 Torr = 0.00135951 kg/cm²10 Torr = 0.0135951 kg/cm²


This conversion table demonstrates how 10 Torr translates into various pressure units, from Pascals to Kilograms per Square Centimeter, facilitating accurate and universal pressure measurements across diverse scientific and technical applications. Each unit caters to specific measurement needs, ensuring precision and consistency in data across fields.

Torr to Pascals (Pa)

1 Torr = 133.322 Pa

Torr converts to pascals, the SI unit for pressure, which is widely used in most scientific and engineering calculations involving force applied over an area.

Torr to Kilopascals (kPa)

1 Torr = 0.133322 kPa

These are larger units of pascals, scaling up for convenience in handling larger or industrial-scale pressures. They are used for applications requiring a broader scale, such as structural engineering and materials science.

Torr to Megapascals (MPa)

1 Torr = 0.000133322 MPa

These are larger units of pascals, scaling up for convenience in handling larger or industrial-scale pressures. They are used for applications requiring a broader scale, such as structural engineering and materials science.

Torr to Bars

1 Torr = 0.00133322 bar

Common in meteorology, the bar is nearly equivalent to atmospheric pressure at sea level. Millibars offer a finer scale, crucial for detailed atmospheric pressure measurements that drive weather prediction models.

Torr to Millibars (mbar)

1 Torr = 1.33322 mbar

Common in meteorology, the bar is nearly equivalent to atmospheric pressure at sea level. Millibars offer a finer scale, crucial for detailed atmospheric pressure measurements that drive weather prediction models.

Torr to Pounds per Square Inch (psi)

1 Torr = 0.0193368 psi

This unit is predominant in the United States for industrial and consumer applications, including automotive tire pressures and hydraulic systems.

Torr to Standard Atmospheres (atm)

1 Torr = 0.00131579 atm

The atm unit is closely aligned with the average atmospheric pressure at sea level, making it practical for studying and modeling atmospheric conditions in environmental sciences.

Torr to Inches of Mercury (inHg)

1 Torr = 0.0393701 inHg

Often used in aviation and meteorology, this unit relates to historical barometric pressure measurements made using mercury columns.

Torr to Inches of Water (inH2O)

1 Torr = 0.53524 inH2O

Typically used in applications involving low pressures, such as in HVAC systems and medical ventilators, where precision in slight pressure variations is crucial.

Torr to Atmospheres (Technical)

1 Torr = 0.00135951 at

A variant of the standard atmosphere, this unit is used primarily in engineering to measure pressures in hydraulic and pneumatic systems.

Torr to Kilograms per Square Centimeter (kg/cm²)

1 Torr = 0.00135951 kg/cm²

This unit is common in some industrial applications outside of the U.S., particularly in hydraulics and materials testing, where it relates pressure directly to weight force per unit area.

What are the Uses of Torr?

Uses of Torr

Vacuum Technology

  • Vacuum Chambers: Torr is used to measure the internal pressure of vacuum chambers in scientific experiments where a near-perfect vacuum is required for accurate results.
  • Vacuum Coating: In industries that apply thin films through vacuum deposition, Torr measurements ensure the vacuum is sufficient to prevent contamination during the coating process.

Medical Applications

  • Hyperbaric Medicine: Torr is utilized to calibrate equipment in hyperbaric oxygen therapy to ensure precise pressure control for therapeutic purposes.
  • Anesthesia Machines: Anesthesiologists use Torr to monitor and adjust the pressure of gases delivered to patients during surgery, ensuring safety and efficacy.

Scientific Research

  • Physics Experiments: Many physics experiments require low pressures, measured in Torr, to study phenomena such as electron mobility without air interference.
  • Space Simulation: Torr is critical in simulating outer space conditions within test chambers, where maintaining and measuring an exact low-pressure environment is necessary.

Industrial Manufacturing

  • Semiconductor Fabrication: Torr measurements are essential in the semiconductor industry to maintain the ultra-clean, low-pressure environments needed for the manufacture of integrated circuits.
  • Food Packaging: Torr is used to measure the vacuum inside packaging to prolong shelf life and prevent spoilage without chemical preservatives.


  • Barometric Pressure Measurement: Although not as common as millibars, Torr is sometimes used in meteorology to measure very precise changes in atmospheric pressure, which can indicate weather changes.


Leak Detection: Engineers use Torr to detect and measure leaks in systems and containers that must be vacuum-sealed for operational integrity, such as in fuel lines or chemical containers.


Why is Torr particularly useful in vacuum applications?

Torr is extremely useful in vacuum applications because it allows for precise measurement of very low pressures, which are common in scientific laboratories and industrial processes that require a controlled vacuum environment.

How does Torr differ from other pressure units like psi or pascal?

Unlike psi, which measures pressure relative to the atmosphere, or pascal, which is the SI unit of pressure, Torr is specifically scaled to the millimeter of mercury measurement. This makes it particularly suitable for applications like vacuum measurements where fine precision is needed.

What are some common fields where Torr is used?

Torr is widely used in fields such as meteorology for high-altitude pressure measurement, aerospace for testing space simulation chambers, and in medical settings for calibrating suction devices and anesthesia equipment.

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