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Vacuum Converter

Convert absolute vacuum readings between pascals, millibar, torr, mmHg, inches of mercury, psia, microns, and percent of full vacuum.

Vacuum

Convert absolute vacuum readings across torr, microns, pressure units, and percent of full vacuum

Compare rough-vacuum, HVAC evacuation, and lab-style absolute pressure readings without mixing them up with gauge pressure.

Quick presets

Reference note

Percent of full vacuum on this page assumes a standard atmospheric reference of 101,325 Pa absolute. Gauge pressure and local weather-corrected vacuum readings need separate interpretation.

Enter values Provide an absolute vacuum reading to calculate all supported equivalents.

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Vacuum converter: torr, microns, absolute pressure, and percent of full vacuum explained

A vacuum converter is useful when one instrument reports absolute pressure in torr, microns, or inches of mercury while another document uses pascals, millibar, psia, or a percent-of-full-vacuum shorthand. The page keeps all of those forms tied to the same absolute pressure reading.

Vacuum readings still describe absolute pressure

A stronger vacuum means a lower absolute pressure, not a higher one. That is why vacuum work often looks numerically inverted compared with everyday pressure work: the better the evacuation, the fewer pascals, torr, or microns remain in the system.

Microns and torr are common because they keep deep-vacuum readings readable. Pascals, millibar, and psia are still the same underlying absolute-pressure measurement in different unit systems.

1 Torr ≈ 133.322 Pa

Core vacuum conversion relationship between the historical torr scale and the SI pressure unit.

% full vacuum = (1 − Pabs / Patm) × 100

Reference relationship used on this page to express the same absolute reading as a percentage of one standard atmosphere removed.

Why percent of full vacuum needs a stated atmosphere reference

Percent of full vacuum is not a separate physical quantity. It is a way of describing how much of one atmosphere has been removed, so it depends on the atmospheric reference chosen for the comparison.

This page uses one standard atmosphere as that reference. That keeps the percentage comparable across SI and imperial pressure units, but it should not be mistaken for a weather-corrected field gauge reading.

When to use torr, microns, or inches of mercury

Torr and microns are common in refrigeration, vacuum pumps, and laboratory evacuation because they keep low absolute pressures readable. Inches of mercury remain common on older vacuum gauges and some service references, while pascals and millibar are common in SI-based documentation.

The safest workflow is to treat every reading as absolute pressure first, then convert it. That avoids the common mistake of mixing vacuum shorthand with gauge pressure assumptions.

Frequently asked questions

Is a higher micron reading a better vacuum?

No. A lower micron reading means lower absolute pressure, which is a deeper vacuum.

 What does 100% vacuum mean on this page?

It means zero absolute pressure relative to one standard atmosphere used as the reference. Real systems approach that limit but do not reach a perfect vacuum in practical service work.

 Why does this page reject values above one atmosphere?

Because the tool is scoped to vacuum levels. Absolute pressures above one atmosphere are valid pressure readings, but they are not vacuum conditions in this converter.

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