Torr is a pressure unit with the symbol Torr. One torr is defined as 1/760 of a standard atmosphere. In Xunits, 1 Torr equals about 133.3223684211 pascals.
Quick facts
- Unit name
- Torr
- Symbol
- Torr
- Quantity
- pressure
- SI bridge
- 1 Torr = 133.322368421 Pa
- Category
- Pressure
- Converter hub
- Pressure converter
Pressure scale
Pressure units are easiest to compare through pascals. This visual places Torr beside neighboring pressure units.
Definition
One torr is defined as 1/760 of a standard atmosphere. In Xunits, 1 Torr equals about 133.3223684211 pascals. Torr and millimeter of mercury are closely related, but modern definitions and practical usage can differ by context. For precise technical work, follow the unit specified by the instrument or standard.
Pressure reference
A pressure number can be gauge, absolute, or differential. The unit Torr tells you the scale, but the surrounding notation tells you the reference. Keep labels such as psig, psia, barg, bara, absolute pressure, or differential pressure when the source provides them.
Exact relationships and reference values
| Relationship | Why it matters |
|---|---|
| 1 Torr = 1/760 atm | Useful reference relationship |
| 760 Torr = 1 atm | Useful reference relationship |
| 1 Torr = about 133.3223684211 Pa | Useful reference relationship |
| 1 Torr = about 0.00131578947 atm | Useful reference relationship |
Where Torr is used
Torr is used in vacuum systems, laboratory equipment, gas handling, vapor pressure, older pressure references, and contexts related to millimeters of mercury.
Common mistakes
- Do not assume Torr is the best unit for ordinary tire or compressor pressure.
- Do not silently replace Torr with mmHg in strict technical documentation.
- Do not ignore whether a vacuum reading is absolute pressure.
Converters and formulas
Use these pages when you need a direct calculation involving Torr.
Related pressure guides
Compare Torr with other pressure units in the same directory.
FAQ
Why is torr used for vacuum?
Torr gives convenient numbers for many low-pressure and vacuum ranges that would be less readable in atmospheres.
How many Torr are in 1 atm?
1 standard atmosphere equals exactly 760 Torr by definition.
Is Torr the same as mmHg?
They are closely related in common usage, but strict definitions and context can matter in technical work.