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Multiple conversions
To convert from torr (torr) to pascal (Pa), use the following formula:
pascal (Pa)
= 101325760000 × 1000× torr (torr)
= 133.32236842105263158× torr (torr)
To convert from torr (torr) to kilopascal (kPa), use the following formula:
kilopascal (kPa)
= 101325760000× torr (torr)
= 0.13332236842105263158× torr (torr)
To convert from torr (torr) to megapascal (MPa), use the following formula:
megapascal (MPa)
= 101325760000 × 11000× torr (torr)
= 0.00013332236842105263158× torr (torr)
To convert from torr (torr) to hectopascal (hPa), use the following formula:
hectopascal (hPa)
= 101325760000 × 10× torr (torr)
= 1.3332236842105263158× torr (torr)
To convert from torr (torr) to millibar (mbar), use the following formula:
millibar (mbar)
= 101325760000 × 10× torr (torr)
= 1.3332236842105263158× torr (torr)
To convert a pressure from torr to bar, multiply by 0.00133322.
One torr is exactly 101,325/760 Pa ≈ 133.322 Pa, and a bar is exactly 100,000 Pa; the ratio is 0.0013332. The two round-number anchors are 750 torr ≈ 1 bar (within 0.01%) and 760 torr = 1.01325 bar exactly, the standard atmosphere.
A freeze-dryer runs at 200 torr during its primary drying stage, and a European qualification document wants the figure in bar:
| torr | bar |
|---|---|
| 1 | 0.00133 |
| 10 | 0.01333 |
| 100 | 0.13332 |
| 250 | 0.33331 |
| 500 | 0.66661 |
| 750 | 0.99992 |
| 760 | 1.01325 |
| 1,000 | 1.33322 |
Torr numbers get small fast — rough vacuum spans 760 down to about 1 torr, high vacuum begins around 10⁻³ torr, and ultra-high vacuum lives below 10⁻⁹ torr — so converting to bar mostly produces long strings of leading zeros (10⁻³ torr is 1.3 × 10⁻⁶ bar). That is why the bar's milli sibling owns European vacuum paperwork instead: 1 torr = 1.333 mbar keeps the digits manageable, and a datasheet's "ultimate pressure 2 × 10⁻³ mbar" meets an American gauge reading of 1.5 × 10⁻³ torr on almost equal terms. The conversion to full bar earns its place at the top of the range, where vacuum work meets ordinary engineering: a 200-torr process step is 0.27 bar absolute, a leak-test differential of 500 torr is 0.67 bar, numbers a pressure-vessel or piping engineer can drop straight into their usual formulas.
Torr figures are absolute by convention — zero is a perfect vacuum. Keep them absolute through the conversion: 0.2667 bar absolute in the example above, which a gauge referenced to the room would show as roughly −0.75 bar. The negative gauge reading and the positive absolute figure describe the same chamber.
To convert from torr (torr) to meter of water @ 4°C (mH2O), use the following formula:
meter of water @ 4°C (mH2O)
= 101325760000 × 19.80665× torr (torr)
= 0.013595098063156391997× torr (torr)
For every practical purpose, torr and millimeters of mercury are the same unit:
The torr was created as a tribute to Evangelista Torricelli, inventor of the mercury barometer, and was originally defined as one millimeter of mercury. Modern metrology split the definitions — the torr is now exactly 1/760 of a standard atmosphere (101,325/760 Pa), while the conventional mmHg is defined through mercury's density as 133.322 Pa — and the two definitions land a hair's breadth apart. This calculator, following its conversion library's rounded constants, reports 1 torr = 1.0000028 mmHg; the physically exact discrepancy is even smaller, about two parts in ten million. No instrument on earth resolves the difference.
A vacuum gauge reads 250 torr and a legacy process sheet wants mmHg:
Done. At six significant figures the calculator shows 250.001 mmHg — a difference with no physical meaning at any realistic precision.
| torr | mmHg |
|---|---|
| 1 | 1.000003 |
| 10 | 10.00003 |
| 100 | 100.0003 |
| 500 | 500.001 |
| 750 | 750.002 |
| 760 | 760.002 |
The practical question is never "how do I convert" but "why do both names exist". Vacuum science and semiconductor processing say torr — chamber base pressures of 10⁻⁶ torr, sputtering recipes at millitorr — while medicine and physiology say mmHg — blood pressure of 120/80, blood-gas tensions, intracranial and intraocular pressures. Same unit, different heritage, and documents almost never mix them; converting between them is really an act of translation between fields. The trap worth flagging sits nearby: neither torr nor mmHg is a millibar. A millibar is 0.750 mmHg, and vacuum equipment sold across the Atlantic often carries one gauge scale in torr and another in mbar — reading the wrong scale introduces a 33% error, which has ruined more than one process run. When a figure's provenance is unclear, anchor on the atmosphere: 760 torr = 760 mmHg = 1,013.25 mbar.
To convert from torr (torr) to pound per square inch (psi), use the following formula:
pound per square inch (psi)
= 101325760000 × 0.00014503768078 × 1000× torr (torr)
= 0.019336767111886184211× torr (torr)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
To convert from torr (torr) to kilopound per square inch (ksi), use the following formula:
kilopound per square inch (ksi)
= 101325760000 × 0.00014503768078× torr (torr)
= 0.000019336767111886184211× torr (torr)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
To convert from torr (torr) to Inch of mercury (inHg), use the following formula:
Inch of mercury (inHg)
= 101325760000 × 0.00014503768078 × 10.000491154× torr (torr)
= 0.039370069493246892442× torr (torr)
With 0.00014503768078 is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
A torr (Torr) is a unit of pressure.
It is primarily used to measure a vacuum, or pressures much lower than the air pressure we experience every day.
While the modern standard (SI) unit for pressure is the pascal (Pa), the torr is still widely used in many scientific and engineering fields.
For conversion, one torr is equal to about 133.32 pascals.
A much simpler way to think about it is in relation to our atmosphere: one standard atmosphere (atm) is defined as exactly 760 Torr.
The unit is named in honor of Evangelista Torricelli, the 17th-century Italian physicist who invented the mercury barometer.
Because of this, one torr was initially defined as being equal to one millimeter of mercury (mmHg).
This means 1 Torr is the pressure exerted by a column of mercury that is one millimeter high.
As mentioned, the torr's most convenient relationship is with the standard atmosphere (atm).
One standard atmosphere—the average air pressure at sea level—is set at exactly 760 Torr.
This straightforward, whole-number conversion makes the torr a popular choice for anyone working with fractions of atmospheric pressure.
The torr is the primary unit of measurement for high-vacuum and ultra-high-vacuum technology.
Because it is such a small unit (it takes 760 of them to equal one atmosphere), it is ideal for quantifying pressures far below normal air pressure.
You will find the torr used in many advanced scientific and industrial fields, including: