How to Convert Millimetres of mercury to PSI (mmHg to psi)
Pressure conversions are used for tyre pressure (psi or bar), blood pressure readings in mmHg and weather maps in millibars. This guide shows how to convert millimetres of mercury into psi by hand, with examples and a quick-reference table.
The conversion
To convert millimetres of mercury to psi, multiply the value by 0.0193367221. To go the other way, divide by the same number (or multiply by 51.7150732812). For a quick estimate, multiply by about 0.019.
PSI = millimetres of mercury × 0.0193367221
Worked examples
- 3 mmHg = 0.05801 psi
- 12.5 mmHg = 0.241709 psi
- 75 mmHg = 1.4503 psi
Millimetres of mercury to PSI table
| Millimetres of mercury | PSI |
|---|---|
| 1 mmHg | 0.019337 psi |
| 2 mmHg | 0.038673 psi |
| 5 mmHg | 0.096684 psi |
| 10 mmHg | 0.193367 psi |
| 20 mmHg | 0.386734 psi |
| 25 mmHg | 0.483418 psi |
| 50 mmHg | 0.966836 psi |
| 100 mmHg | 1.9337 psi |
| 250 mmHg | 4.8342 psi |
| 500 mmHg | 9.6684 psi |
| 1,000 mmHg | 19.3367 psi |
Common questions
Is mmHg to psi exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the PSI to Millimetres of mercury converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Forgetting squared and cubed units
Area and volume factors are the length factor squared or cubed, so 1 m² is about 10.76 sq ft, not 3.28.
Background
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For any value, use the Millimetres of mercury to PSI Converter or browse all pressure converters.
Run your own numbers: Millimetres of mercury to PSI Converter