mmHg to PSI Converter
Millimeters of mercury (mmHg) is a traditional pressure unit based on the height of a mercury column. It is equivalent to the torr (1 mmHg ≈ 1 Torr). Standard atmospheric pressure...
Formula
Source: Engineering Toolbox, NIST | Last reviewed: June 8, 2026
Examples
760 mm Hg
= 14.7 psi
Standard atmospheric pressure
1 mm Hg
= 0.0193 psi
1 mmHg = 0.0193 psi
100 mm Hg
= 1.93 psi
500 mm Hg
= 9.67 psi
Typical rough vacuum range
Quick Reference Table
| mmHg | PSI |
|---|---|
| 1 | 0.019 |
| 10 | 0.193 |
| 100 | 1.93 |
| 500 | 9.67 |
| 760 | 14.7 |
| 1000 | 19.34 |
| 1520 | 29.39 |
Where is this used?
Vacuum system specifications: vacuum gauges often read in mmHg.
Barometric pressure: standard sea-level pressure of 760 mmHg = 14.696 psi for pressure vessel vacuum ratings.
Frequently Asked Questions
Is mmHg the same as torr?
For all practical purposes, yes. 1 mmHg ≈ 1.000000142 Torr. The difference is less than 0.2 parts per million. In industrial and medical applications, they are used interchangeably.
Why is mercury used as a pressure reference?
Mercury has a high density (13.6× water), so a practical column height (760 mm) can measure atmospheric pressure. A water column would need to be 10.3 m tall for the same range. Mercury's low vapor pressure also makes it ideal for precise measurements.
How do negative mmHg values convert?
Negative mmHg values represent vacuum (pressure below atmospheric). For example, -760 mmHg (perfect vacuum) = -14.7 psig = 0 psia. The linear conversion factor works identically for negative values.
Reviewed for accuracy
· Last reviewed: June 8, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.