How to Convert Millimetres of mercury to Millibars (mmHg to mbar)
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 millibars by hand, with examples and a quick-reference table.
The conversion
To convert millimetres of mercury to millibars, multiply the value by 1.33322. To go the other way, divide by the same number (or multiply by 0.7500637554). For a quick estimate, multiply by about 1.3.
Millibars = millimetres of mercury × 1.33322
Worked examples
- 3 mmHg = 3.9997 mbar
- 12.5 mmHg = 16.6653 mbar
- 75 mmHg = 99.9915 mbar
Millimetres of mercury to Millibars table
| Millimetres of mercury | Millibars |
|---|---|
| 1 mmHg | 1.3332 mbar |
| 2 mmHg | 2.6664 mbar |
| 5 mmHg | 6.6661 mbar |
| 10 mmHg | 13.3322 mbar |
| 20 mmHg | 26.6644 mbar |
| 25 mmHg | 33.3305 mbar |
| 50 mmHg | 66.661 mbar |
| 100 mmHg | 133.322 mbar |
| 250 mmHg | 333.305 mbar |
| 500 mmHg | 666.61 mbar |
| 1,000 mmHg | 1,333.22 mbar |
Common questions
Is mmHg to mbar 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 Millibars to Millimetres of mercury converter.
Mistakes to avoid
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
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
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
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.
Many conversion factors are exact by definition. The inch has been defined as exactly 2.54 centimetres since 1959, and the pound as exactly 0.45359237 kilograms, so conversions involving them can be as precise as you need.
For any value, use the Millimetres of mercury to Millibars Converter or browse all pressure converters.
Run your own numbers: Millimetres of mercury to Millibars Converter