Torr to psi Converter
1 Torr = 1/760 of a standard atmosphere exactly (by definition), and 1 atm = 14.695948775 psi. Therefore 1 Torr = 14.695948775 / 760 = 0.0193367747 psi. The torr is named after...
Formula
Source: NIST SP 811, ISO 3529 (Vacuum technology, Vocabulary) | Last reviewed: June 27, 2026
Examples
1 Torr
= 0.01934 psi
1 Torr = 0.01934 psi
760 Torr
= 14.696 psi
760 Torr = 14.696 psi (standard atmospheric pressure)
100 Torr
= 1.934 psi
100 Torr ≈ 1.93 psi, vacuum distillation range
10 Torr
= 0.1934 psi
10 Torr ≈ 0.193 psi, thin-film evaporation
Quick Reference Table
| Torr | psi | Vacuum Range Description |
|---|---|---|
| 760 | 14.696 | Atmospheric pressure (standard) |
| 500 | 9.67 | Rough vacuum |
| 100 | 1.934 | Medium vacuum (vacuum distillation) |
| 10 | 0.1934 | Medium vacuum (thin-film evaporation) |
| 1 | 0.01934 | High vacuum |
| 0.1 | 0.001934 | High vacuum (freeze-drying) |
| 0.001 | 0.0000193 | Ultra-high vacuum (semiconductor) |
Where is this used?
Therefore 1 Torr = 14.695948775 / 760 = 0.0193367747 psi.
The torr is named after Evangelista Torricelli, the Italian physicist who invented the barometer in 1643.
For most practical purposes, 1 Torr ≈ 1 mmHg (millimeter of mercury), though the precise definition of 1 Torr = 1/760 atm differs from 1 mmHg = 13.5951 × 9.80665 × 0.001 = 0.01933678 psi by less than 0.000015%.
The torr is the universal unit in vacuum technology, the entire vacuum range from atmospheric pressure (760 Torr) to ultra-high vacuum (10⁻¹² Torr) uses torr or mbar as the primary pressure unit.
US vacuum pump manufacturers (Edwards, Leybold, Varian/Agilent, Pfeiffer Vacuum) rate pump performance in Torr or mbar, but the US process engineer connecting the vacuum system to a pressure vessel rated in psi must convert.
A vacuum vessel designed for full vacuum service (ASME BPVC Section VIII Division 1, external pressure design, typically rated for 15 psi external) must withstand atmospheric pressure (760 Torr = 14.7 psi) when evacuated.
The relationship 760 Torr = 14.7 psi (atmospheric pressure) is one of the key pressure reference equivalences in engineering.
In vacuum distillation and thin-film evaporation, the operating pressure is typically 1-100 Torr (0.019-1.93 psi absolute).
A wiped-film evaporator operating at 10 Torr absolute converts to 0.193 psi absolute, far below atmospheric, requiring vacuum pump capacity calculation.
In lyophilization (freeze-drying), the chamber pressure during primary drying is typically 0.1-0.5 Torr (0.0019-0.0097 psi), and the ice condenser (cold trap) operates at even lower pressures.
These extremely low absolute pressures in psi illustrate why the torr is a more practical unit for vacuum work, 0.1 Torr is a readable number, while 0.0019 psi requires scientific notation.
However, the vessel's ASME nameplate is in psi (or psia for absolute), so the operating torr must be converted to verify the vessel is operated within its design pressure limits.
In semiconductor manufacturing (CVD, PVD, etch processes), process chamber pressures are typically 1 mTorr to 10 Torr (0.000019 to 0.19 psi), values that are difficult to express in psi but straightforward in torr or mTorr.
The torr also appears in medical vacuum systems: NFPA 99 specifies medical-surgical vacuum systems at 15-19 inHg gauge (approximately 380-480 Torr absolute), and converting the system operating pressure to psi for the ASME pressure vessel registration requires torr-to-psi conversion.
Real-World Usage Scenarios
Vacuum distillation column design verification
A pharmaceutical manufacturer operates a vacuum distillation column for active pharmaceutical ingredient (API) purification. The column operates at 5 Torr absolute pressure (0.0967 psi absolute) at the top, with a bottoms temperature of 180°C. The column is an ASME BPVC Section VIII Division 1 pressure vessel designed for full vacuum external pressure (15 psi) on the shell side. The internal operating pressure of 0.0967 psi absolute = −14.60 psig (relative to atmospheric). The vessel must withstand the external pressure differential of 14.60 psig without buckling, this is the external pressure design calculation per UG-28 of the BPVC. The design calculation requires the operating pressure in psia (or psig), not in torr, the torr-to-psi conversion (× 0.01934) is performed at every operating condition verification. A 1% error in the conversion (using 0.0195 instead of 0.01934) translates to 0.15 psi error in the external pressure, small individually but cumulative over the vessel's 30-year design life. The vessel's fabrication quality and inspection requirements depend on the precise external pressure design, and the conversion error could affect the as-built documentation's compliance with the BPVC requirements.
Industry Standards Referenced
Frequently Asked Questions
Is 1 Torr the same as 1 mmHg?
For all practical engineering purposes, yes. 1 Torr is defined as exactly 1/760 of a standard atmosphere (14.69595 psi). 1 mmHg (conventional millimeter of mercury) is the pressure exerted by a 1 mm column of mercury at 0°C under standard gravity, which computes to 0.01933678 psi, differing from 1 Torr (0.01933677 psi) by about 0.000015%. The difference is negligible for all industrial and laboratory vacuum work. The unit 'Torr' was adopted internationally in 1954 to replace the slightly ambiguous 'mmHg' in vacuum technology.
Why use Torr instead of psi for vacuum?
Because vacuum pressures span 15 orders of magnitude from atmosphere (10³ Torr) to ultra-high vacuum (10⁻¹² Torr), and the torr scale produces human-readable numbers across this range. Expressing 10⁻⁶ Torr as 1.9 × 10⁻⁸ psi is technically correct but thoroughly impractical. The torr (and its subdivision, the millitorr or micron: 1 mTorr = 0.001 Torr = 1 micron of mercury) provides a practical logarithmic scale: rough vacuum (760-1 Torr), medium vacuum (1-10⁻³ Torr), high vacuum (10⁻³-10⁻⁹ Torr), ultra-high vacuum (<10⁻⁹ Torr). US engineers working at the vacuum/pressure interface must be fluent in both torr and psi.
What does this converter do?
This converter performs the unit conversion at standard conditions using the exact conversion factor. The result is displayed with appropriate precision for engineering use.
Reviewed for accuracy
Verified against NIST pressure standards and ISO vacuum definitions · Last reviewed: June 27, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.