Vacuum Fundamentals: Units, Ranges & How It Works

Vacuum is simply a space where gas pressure is lower than normal atmospheric pressure. In industrial and laboratory settings, creating and controlling that reduced pressure is what enables processes ranging from vacuum packaging and drying to semiconductor fabrication and leak testing. Before selecting a pump, gauge or fitting, it helps to understand the basic units and ranges the industry works in.

What "Vacuum" Actually Means

Standard atmospheric pressure at sea level is approximately 1,013 mbar (roughly 760 Torr, or 101,325 Pa). Any pressure below that is technically a vacuum. The deeper the vacuum, the fewer gas molecules remain in a given space — which is why different vacuum levels require fundamentally different pump technologies and sealing approaches.

Common Units of Measurement

Vacuum level is expressed in several units depending on region and industry convention. The most common are:

• mbar (millibar) — the most widely used unit in European and Middle Eastern industrial contexts
• Torr — common in North American laboratory and semiconductor settings (1 Torr ≈ 1.333 mbar)
• Pascal (Pa) — the SI unit (1 mbar = 100 Pa)
• Micron (mTorr) — used for very high vacuum levels, where finer resolution is needed

MILLIBAR's product specifications default to mbar, since it's the standard across most of the GCC, Middle East and Africa region, but our team can convert and confirm any spec in the unit your process documentation uses.

The Vacuum Range Spectrum

Not all vacuum is the same. The industry generally divides it into five broad ranges, each requiring different pump technology:

• Rough / Low Vacuum — 1,000 to 1 mbar. Typical for packaging, general drying and basic material handling. Rotary vane and diaphragm pumps operate well here.
• Medium Vacuum — 1 to 10⁻³ mbar. Common in distillation, degassing and many laboratory applications. Often requires two-stage or dry pump technology.
• High Vacuum — 10⁻³ to 10⁻⁷ mbar. Used in semiconductor processing, coating and analytical instrumentation. Typically requires a backing pump paired with a high-vacuum stage such as a turbomolecular or diffusion pump.
• Ultra-High Vacuum (UHV) — 10⁻⁷ to 10⁻¹² mbar. Reserved for specialized research and advanced semiconductor work, where even trace outgassing from chamber materials becomes significant.
• Extreme High Vacuum — below 10⁻¹² mbar. Rare outside of fundamental physics research.

Why the Range Matters for Equipment Selection

The vacuum range your process actually requires determines almost everything downstream: pump technology, seal material, fitting standard (KF, ISO or CF), and even the gauge type needed to measure it accurately. Specifying a pump rated far beyond what your process needs adds unnecessary cost; underspecifying leads to processes that never reach the pressure they require. This is why MILLIBAR's sourcing process always starts with the actual application and target pressure, not the product catalog.

Sealing and Leak-Tightness

As vacuum level deepens, the tolerance for leaks tightens dramatically. A rough-vacuum packaging line can accommodate minor imperfections that would be completely unacceptable in a high-vacuum semiconductor chamber. This is also why helium leak detection becomes increasingly important as processes move into medium and high vacuum ranges — even microscopic leaks can prevent a system from ever reaching its target pressure.

Getting the Right Fit

If you're specifying vacuum equipment for the first time, the most useful information to have ready is: the target pressure range, the gas or process media involved, operating temperature, and whether the process runs continuously or intermittently. With those four details, our team can typically narrow down a suitable technology category quickly — the same logic behind our SmartSource tool.