Vacuum is measured as an absolute pressure below atmosphere, and the lower the number, the deeper the vacuum. The common units are the millibar (mbar), Torr, pascal (Pa) and, in the US, microns and PSI. As a quick guide: 1 mbar = 0.75 Torr = 100 Pa, and atmospheric pressure is about 1013 mbar (760 Torr).
The main vacuum units at a glance
| Unit | Equivalent | Where it’s used |
|---|---|---|
| 1 mbar (hPa) | 0.75 Torr = 100 Pa = 0.75 mmHg | Europe / UK standard |
| 1 Torr | 1 mmHg = 1.33 mbar = 133.3 Pa | US, scientific |
| 1 pascal (Pa) | 0.01 mbar = 0.0075 Torr | SI unit |
| 1 micron (millitorr) | 10-3 Torr = 1.33×10-3 mbar | US, deep vacuum |
| Atmosphere | 1013 mbar = 760 Torr = 101,325 Pa | Reference point |
Why lower means deeper
Vacuum is the absence of gas, so as you remove gas the pressure falls. A pump quoted at an ultimate pressure of 2×10-3 mbar reaches a far deeper vacuum than one quoted at 0.5 mbar. Pressures are often written in scientific notation (10-3 mbar) because they span many orders of magnitude — see our guide to vacuum ranges.
mbar vs Torr vs micron
mbar and Torr are the two you’ll meet most. They’re close but not equal: 1 Torr is about 1.33 mbar. Microns (millitorr) appear on US gauges for deep vacuum — 1000 microns = 1 Torr. If a datasheet mixes units, convert to one before comparing pumps.
Real pump specs, converted
Datasheets don’t always use the unit you’re comparing in. Here are ultimate-pressure specs for pumps we work with, in both mbar and Torr, so you can compare across brands and units directly:
| Pump | Ultimate pressure (mbar) | Ultimate pressure (Torr) |
|---|---|---|
| Edwards nES (single-stage rotary vane) | 0.5 mbar | ≈0.375 Torr |
| DVP RC.8M (single-stage rotary vane) | 0.1 mbar | ≈0.075 Torr |
| Edwards E2S (two-stage rotary vane) | 2×10-3 mbar | ≈1.5×10-3 Torr |
| Edwards EDP (dry chemical) | <1 mbar | <0.75 Torr |
| Busch MINK (claw) | 60 mbar | ≈45 Torr |
| Leybold TURBOVAC i (turbomolecular) | ≤8×10-8 mbar | ≈6×10-8 Torr |
| Leybold TURBOVAC iX (turbomolecular) | ≤5×10-10 mbar | ≈3.75×10-10 Torr |
Figures from manufacturer datasheets; Torr values converted at 1 mbar = 0.75 Torr and rounded. See our Leybold TURBOVAC guide and Edwards E2M/E2S service guide for more on these pumps.
Which unit should you use?
In the UK and Europe, mbar is the practical standard and what most Edwards, Leybold and MIL’S datasheets quote. Whatever unit you use, compare like with like — and remember that pumping speed and ultimate pressure are two different specifications.
Need help comparing pump specifications?
Send us the datasheets or your requirement and we’ll translate the numbers and recommend the right pump. Email [email protected] or request a quote.
Frequently asked questions
What is the difference between mbar and Torr?
They are both units of pressure. 1 Torr equals about 1.33 mbar (1 mbar = 0.75 Torr). mbar is standard in the UK and Europe; Torr is common in the US and in science.
What is a micron of vacuum?
A micron is one micrometre of mercury, equal to one millitorr (10^-3 Torr, about 1.33×10^-3 mbar). It is used on US gauges to express deep vacuum; 1000 microns equals 1 Torr.
Does a lower pressure mean a deeper vacuum?
Yes. Vacuum is measured as absolute pressure, so a lower number means less gas remains and a deeper vacuum. 2×10^-3 mbar is a much deeper vacuum than 0.5 mbar.
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.