torr
Pressureexact by definition
The torr is exactly 1/760 of a standard atmosphere, which is exactly 101325/760 pascals, or about 133.3224 Pa. It is the working unit of vacuum technology in North America, where pumps, gauges and process recipes are all specified in torr and millitorr.
Watch out: The torr and the conventional millimetre of mercury are NOT the same unit, though they agree to seven significant figures. The mmHg is defined from a fluid of density 13595.1 kg/m³ under standard gravity, giving 133.322387415 Pa; the torr is defined as a pure fraction of the atmosphere, giving 133.3223684 Pa. The difference is about one part in seven million, irrelevant to a blood pressure cuff and occasionally relevant to a calibration laboratory.
| 1 | 0.13332237 |
Named for Evangelista Torricelli, who built the first mercury barometer in 1643 and understood that the column was held up by the weight of the atmosphere rather than by a horror of the void.
One torr in every pressure unit
| 1,333.22 | microbar (μbar) | |
| 1,333.22 | barye (Ba) | |
| 1,000 | millitorr (mTorr) | |
| 133.322 | pascal (Pa) | |
| 13.5951 | millimeter of water column (mmH₂O) | |
| 2.7845 | pound per square foot (lb/ft²) | |
| 1.35951 | centimeter of water column (cmH₂O) | |
| 1.33322 | hectopascal (hPa) | |
| 1.33322 | millibar (mbar) | |
| 1 | torr (Torr)this unit | |
| 1 | millimeter of mercury (mmHg) | |
| 0.53524 | inch of water column (in w.g.) | |
| 0.133322 | kilopascal (kPa) | |
| 0.0446033 | foot of water column (ft H₂O) | |
| 0.0393701 | inch of mercury (inHg) | |
| 0.0193368 | pound per square inch (psi) | |
| 0.0135951 | meter of water column (m H₂O) | |
| 0.0133322 | decibar (dbar) | |
| 0.00135951 | kilogram-force per square centimeter (kgf/cm²) | |
| 0.00133322 | bar (bar) | |
| 0.00131579 | atmosphere (atm) | |
| 0.000133322 | megapascal (MPa) | |
| 0.0000193368 | kip per square inch (ksi) | |
| 1.33322e-07 | gigapascal (GPa) | |
| 1.93368e-08 | million pounds per square inch (Mpsi) |