Vacuum is divided into four ranges: rough (atmosphere to ~1 mbar), medium (1 to 10-3 mbar), high (10-3 to 10-7 mbar) and ultra-high vacuum, UHV (below 10-7 mbar). Each range needs different pump technology, and high and ultra-high vacuum always need a backing pump beneath the main pump.
The four vacuum ranges
| Range | Pressure | Typical pumps | Example uses |
|---|---|---|---|
| Rough (low) | 1013–1 mbar | Diaphragm, single-stage rotary vane, claw, liquid ring | Filtration, packaging, degassing |
| Medium | 1–10-3 mbar | Two-stage rotary vane, scroll | Freeze-drying, general lab vacuum |
| High | 10-3–10-7 mbar | Turbomolecular, diffusion (with backing pump) | Analytical instruments, coating |
| Ultra-high (UHV) | below 10-7 mbar | Turbomolecular + cryo/ion (with backing pump) | Surface science, semiconductors |
Why you combine pumps
No single pump spans every range. A high-vacuum pump such as a turbomolecular pump cannot exhaust to atmosphere on its own, so it sits on a backing (roughing) pump — typically a rotary vane or scroll pump — that takes the exhaust down to a pressure the turbo can handle.
Which range do you need?
Your process sets the range: filtration and packaging live in rough vacuum; freeze-drying in medium; analytical instruments and coating in high or ultra-high. Once you know the range, the pump type follows. Pressures are written in mbar or Torr; deeper vacuum means a lower number.
Which vacuum range does your process need?
Tell us the application and we’ll identify the range and the right pump combination. Email [email protected] or request a quote.
Frequently asked questions
What are the four vacuum ranges?
Rough vacuum (atmosphere to about 1 mbar), medium vacuum (1 to 10^-3 mbar), high vacuum (10^-3 to 10^-7 mbar) and ultra-high vacuum or UHV (below 10^-7 mbar).
What is ultra-high vacuum?
Ultra-high vacuum (UHV) is pressure below 10^-7 mbar, used in surface science and semiconductor work. It is reached with a turbomolecular pump (often with a cryo or ion pump) on a backing pump.
Which vacuum pump is used for high vacuum?
Turbomolecular and diffusion pumps reach high vacuum (10^-3 to 10^-7 mbar), but both need a backing pump such as a rotary vane or scroll pump to operate.
Written by the Girovac technical team. Girovac Ltd has supplied and serviced industrial and laboratory vacuum equipment from its North Walsham workshop since 1983. Last updated: July 2026.