Vacuum Unit Conversion Calculator

Convert between different vacuum pressure units quickly. Enter a value in any unit to see equivalent values in all other common vacuum measurement units.

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Understanding Vacuum Pressure Units

Vacuum pressure is measured in various units depending on the application and region. Understanding these units and being able to convert between them is essential for scientific, industrial, and engineering applications involving vacuum systems.

Common Vacuum Pressure Units

  • Torr: Named after Evangelista Torricelli, 1 Torr is approximately equal to the pressure exerted by 1 mmHg.
  • Millibar (mbar): Commonly used in meteorology and in many European countries. 1 bar = 1000 mbar.
  • Pascal (Pa): The SI unit of pressure. 1 Pa = 1 N/m².
  • Inches of Mercury (inHg): Often used in barometric pressure measurements, especially in aviation.
  • Pounds per square inch (psi): Common in the United States for various pressure measurements.

Conversion Factors

Here are some key conversion factors between common vacuum units:

  • 1 atm = 760 Torr = 1013.25 mbar = 101325 Pa = 14.696 psi = 29.92 inHg
  • 1 Torr = 1.33322 mbar = 133.322 Pa = 0.0193368 psi = 0.0393701 inHg
  • 1 mbar = 0.750062 Torr = 100 Pa = 0.0145038 psi = 0.0295300 inHg
  • 1 psi = 51.7149 Torr = 68.9476 mbar = 6894.76 Pa = 2.03602 inHg

Frequently Asked Questions

What is the difference between absolute pressure and gauge pressure?

Absolute pressure is measured relative to a perfect vacuum (zero pressure), while gauge pressure is measured relative to atmospheric pressure. Vacuum measurements are typically absolute pressure measurements.

Why are there so many different vacuum pressure units?

Different industries and regions developed their own standard units over time. Scientific applications often use Torr or Pascal, while industrial applications might use psi or inHg, and meteorological applications typically use mbar or hPa.

How do I measure vacuum pressure?

Vacuum pressure is measured using specialized instruments like manometers, capacitance manometers, or vacuum gauges (Pirani, thermocouple, or ionization gauges for different pressure ranges).

What is considered a high vacuum?

High vacuum typically refers to pressures below 10-3 Torr (1 mTorr). Ultra-high vacuum is below 10-9 Torr.

Can I use this calculator for positive pressure conversions?

Yes, this calculator works for both vacuum (below atmospheric) and positive pressure (above atmospheric) conversions, though it's primarily designed with vacuum applications in mind.

What's the most accurate unit for vacuum measurement?

Accuracy depends more on the measurement device than the unit. The Pascal is the SI unit and is generally preferred for scientific work, but Torr is also widely used in vacuum science.

How does altitude affect vacuum measurements?

At higher altitudes, atmospheric pressure is lower, which affects gauge pressure measurements but not absolute pressure measurements. This calculator uses absolute pressure values.

What units are used for extremely high vacuum?

For very high vacuum (UHV) ranges, pressure is often expressed in scientific notation (e.g., 10-9 Torr) or using prefixes like nanoTorr (nTorr).

Why is mercury (mmHg, inHg) commonly used in pressure measurements?

Mercury was historically used because its high density allows for reasonably sized manometers. The Torr unit originates from early mercury column measurements.

How often should I calibrate my vacuum measurement equipment?

Calibration frequency depends on usage and required accuracy. Industrial applications might calibrate annually, while research labs might calibrate more frequently. Always follow manufacturer recommendations.