Inches of Mercury to PSI Converter
1 inch of mercury (inHg) equals 0.49115 psi. Mercury manometers were historically the standard for pressure measurement because mercury is dense (13.6× water), allowing compact...
Formula
Source: Engineering Toolbox | Last reviewed: June 7, 2026
Examples
1 in Hg
= 0.4912 psi
1 inHg = 0.491 psi
29.92 in Hg
= 14.7 psi
Standard atmosphere at sea level
10 in Hg
= 4.912 psi
Quick Reference Table
| inHg | psi |
|---|---|
| 1 | 0.49 |
| 5 | 2.46 |
| 10 | 4.91 |
| 15 | 7.37 |
| 20 | 9.82 |
| 29.92 | 14.7 |
Where is this used?
Frequently Asked Questions
Why is mercury still used despite its toxicity?
Mercury instruments are largely phased out in favor of digital and aneroid devices. However, inHg remains a common unit for barometric pressure in aviation, weather reporting, and legacy vacuum systems.
How do I convert inHg to kPa?
Multiply inHg by 3.38639. Standard atmospheric pressure: 29.92 inHg = 101.325 kPa.
What is the difference between inHg and inH₂O?
Mercury is 13.6× denser than water. 1 inHg = 13.6 inH₂O. For low pressures, inH₂O gives better resolution; for barometric, inHg is standard.
Reviewed for accuracy
· Last reviewed: June 7, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.