In 1 pounds per square inch there are 51,714.930373 millitorr. Meanwhile in 1 millitorr there are 0.0000193368 pounds per square inch. Keep reading to learn more about each unit of measure and how they are calculated. Or just use the Millitorr to Pounds per square inch calculator above to convert any number.
* Values rounded to 6 decimal places for readability
To convert pounds per square inch (psi) to millitorr (mTorr), use a fixed pressure conversion.
Example:
If you have 2 psi, then: 2 × 51,714.932 = 103,429.864 mTorr
For the reverse conversion:
Tip: This is a pressure unit conversion. It does not change the pressure, only the unit label.
PSI stands for pounds per square inch. It measures force spread over one square inch of area. In many settings, PSI is used for tires, air tools, tanks, and gas lines.
A millitorr is a unit of pressure used for vacuum levels. It equals one-thousandth of a torr (0.001 Torr). Labs and vacuum systems often use mTorr because it fits low-pressure ranges well.
PSI is common near normal air pressure and above. Millitorr is common far below normal air pressure. They measure the same thing (pressure) but fit different ranges.
A common conversion is:
This value comes from standard unit links between psi, pascals, and torr.
There are 51,714.932571 mTorr in 1 PSI.
That means even a small change in PSI equals a large change in mTorr.
Use this formula:
Example:
Use the inverse formula:
Example:
It depends on the source. Many PSI readings are PSIG (gauge), which is relative to local air pressure. Vacuum units like mTorr are usually absolute pressure.
If you convert PSIG straight to mTorr, the result can be wrong for vacuum work. Use PSIA (absolute) when you need a true pressure conversion.
Use:
At sea level, atmospheric pressure is about:
Example:
Then convert PSIA to mTorr using the PSI to mTorr formula.
If the value is 0 psia, that is a perfect vacuum in theory:
If the value is 0 psig, that means normal air pressure, not vacuum:
At sea level, standard atmospheric pressure is about:
These are both “one atmosphere” in different units.
Millitorr is a very small unit, made for vacuum work. PSI is larger and used for higher pressures. Since 1 psi is a lot of pressure in vacuum terms, the mTorr number looks big.
This conversion comes up in vacuum and gas work, such as:
No. Unit conversion does not change with temperature. The same PSI always equals the same mTorr.
Temperature can change the pressure in a sealed system, but that is a physics effect, not a unit change.
Rounding depends on what you need. For most practical use, 2 to 4 decimal places in PSI is already very precise. For mTorr, rounding to whole numbers is often fine unless you work at very low pressure.
The Calculate Box tool to convert pounds per square inch to millitorr uses the open source script Convert.js to convert units of measurement. To use this tool, simply type a pounds per square inch value in the box and have it instantly converted to millitorr.