psi to Torr Converter
1 psi = 51.71493257 Torr exactly (since 760 Torr / 14.695948775 psi = 51.7149). The psi-to-torr conversion is the bridge from US pressure specifications, where psi is the universal...
Formula
Source: NIST SP 811, ISO 80000-4 | Last reviewed: June 27, 2026
Examples
1 psi
= 51.71 Torr
1 psi = 51.71 Torr
14.696 psi
= 760 Torr
14.696 psi = 760 Torr (atmospheric pressure)
30 psi
= 1551 Torr
30 psig ≈ 1,551 Torr (≈ 2 atm absolute)
150 psi
= 7757 Torr
150 psig ≈ 7,757 Torr (≈ 10.2 atm absolute, typical ASME relief valve setpoint)
Quick Reference Table
| psi | Torr | atm (approx) | Context |
|---|---|---|---|
| 1 | 51.7 | 0.068 | Low pressure |
| 14.7 | 760 | 1 | Atmospheric pressure |
| 30 | 1551 | 2.04 | Typical compressed air system |
| 100 | 5171 | 6.8 | Industrial compressed air (100 psig) |
| 150 | 7757 | 10.2 | ASME Class 150 flange rating |
| 1000 | 51715 | 68 | High-pressure hydraulics |
| 3000 | 155145 | 204 | Ultra-high-pressure hydraulics |
Where is this used?
The psi-to-torr conversion is the bridge from US pressure specifications, where psi is the universal unit for everything from tire pressure to hydraulic systems to pressure vessels, to the vacuum technology world where torr dominates.
The factor 51.715 is worth knowing for quick mental conversion: 1 psi ≈ 51.7 Torr, so 30 psi ≈ 1,550 Torr (about 2 atmospheres).
A US pressure relief valve set at 150 psi corresponds to 150 × 51.715 = 7,757 Torr, equivalent to about 10.2 atmospheres.
In the reverse context (vacuum), a vacuum system pulling down to 10 Torr has a US gauge pressure of approximately −14.5 psig (10 Torr = 0.19 psia, so psig = 0.19 − 14.7 = −14.5 psig).
The psi-to-torr conversion is particularly important when US pressure vessel and piping codes (ASME B31.3, ASME BPVC) specify design and test pressures in psi, but the process operating conditions are in torr (as is typical for vacuum processes).
A vessel with an ASME nameplate rating of 'MAWP: 50 psi @ 650°F, FV (full vacuum)' operates at 50 psig internal and full vacuum (15 psi external), and the process engineer must verify that the vacuum distillation operating pressure of 50 Torr (0.97 psia) is well within the vessel's vacuum rating.
In leak testing, the pressure differential driving a leak is expressed in psi (for the US pressure test code, ASME BPVC Section V Article 10) or in torr or mbar (for the vacuum-side helium leak detector).
A helium leak test at 15 psi internal pressure with the vacuum-side detector reading 10⁻⁹ atm·cc/s He, the 15 psi driving force is 15 × 51.715 = 776 Torr, and the leak rate sensitivity is proportional to the square root of the pressure differential (for molecular flow leaks), making the psi-to-torr conversion necessary for the leak rate extrapolation from test conditions to operating conditions.
Real-World Usage Scenarios
Vacuum pump capacity specification
A US semiconductor manufacturer specifies a vacuum pump for a new CVD (chemical vapor deposition) tool. The CVD process requires a base pressure of 1 mTorr (0.001 Torr) and a process pressure of 100 mTorr (0.1 Torr) during deposition. The pump's ultimate pressure specification is 10⁻⁸ Torr, close to the UHV range. The pump's pumping speed is 1,000 L/s. The US engineering team converts all the metric (torr, L/s) values to US customary for the facility engineering documentation: base pressure 1 mTorr = 0.001 Torr = 0.001 × 51.715 / 1000 = 5.17 × 10⁻⁵ psi (a very small number, impractical to use in US equipment specs, the value is left in torr). Process pressure 100 mTorr = 0.1 × 51.715 / 1000 = 5.17 × 10⁻³ psi (still very small). The pump speed 1,000 L/s = 1 m³/s = 35.31 ft³/s = 2,119 CFM. The vacuum system is a hybrid: process pressures in torr (international standard for vacuum), but the pump's exhaust and the mechanical equipment schedules in psi and CFM (US standard). The psi-to-torr conversion is performed at every interface, but the actual vacuum work uses torr exclusively. The conversion to psi is implicit in the cost analysis (electricity cost is in $/kWh, equipment cost is in $, pressure vessel codes reference psi for the atmospheric collapse design pressure).
Industry Standards Referenced
Frequently Asked Questions
Why does 1 psi = 51.7 Torr seem so large?
Because the torr is a very small unit, it's 1/760 of an atmosphere (the pressure of a 1 mm column of mercury). The psi is a much larger unit (the pressure of a 1-inch square column of mercury about 2.036 inches tall). So 1 psi represents the same pressure as a 51.7 mm column of mercury, hence 51.7 Torr. This illustrates why the torr is impractical for high-pressure work (1,000 psi = 51,700 Torr, unwieldy) and psi is impractical for vacuum work (10⁻⁶ Torr = 0.000000019 psi, also unwieldy).
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.
How accurate is the conversion?
The conversion factor used is exact or to four significant figures depending on the units. For most engineering calculations, the precision is more than sufficient. For precision work, consult the relevant NIST or ISO standards referenced on this page.
Reviewed for accuracy
Verified against NIST pressure conversion standards · 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.