"Vacuum degree" as the name implies is the degree of vacuum.
The so-called "vacuum" refers to the gas state where the pressure is lower than 101325 Pascal (that is, a standard atmospheric pressure of about 101KPa) in a given space .
In a vacuum state, the rarefaction of the gas is usually expressed by the pressure value of the gas. Obviously, the smaller the pressure value, the thinner .
Commonly used vacuum degree unit conversion table:
| unit | kPa | inches of mercury | mm Hg | standard atmospheric pressure | show tolerance |
| 1 bar Bar | 100KPa | KPa''Hg | 750mmHg | 0.987atm | ±2.5% |
