How to Convert Millibars to PSI (mbar 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 millibars into psi by hand, with examples and a quick-reference table.
The conversion
To convert millibars to psi, multiply the value by 0.0145037744. To go the other way, divide by the same number (or multiply by 68.94757). For a quick estimate, multiply by about 0.015.
PSI = millibars × 0.0145037744
Worked examples
- 3 mbar = 0.043511 psi
- 12.5 mbar = 0.181297 psi
- 75 mbar = 1.0878 psi
Millibars to PSI table
| Millibars | PSI |
|---|---|
| 1 mbar | 0.014504 psi |
| 2 mbar | 0.029008 psi |
| 5 mbar | 0.072519 psi |
| 10 mbar | 0.145038 psi |
| 20 mbar | 0.290075 psi |
| 25 mbar | 0.362594 psi |
| 50 mbar | 0.725189 psi |
| 100 mbar | 1.4504 psi |
| 250 mbar | 3.6259 psi |
| 500 mbar | 7.2519 psi |
| 1,000 mbar | 14.5038 psi |
Common questions
Is mbar 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 Millibars converter.
Mistakes to avoid
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.
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Mixing similar-sounding units
US and imperial gallons, pints and tons are different sizes, and decimal kilobytes differ from binary kibibytes.
Background
For everyday use, three or four significant figures are usually enough. Engineering, science and trade documents may need more, and rounding should happen only at the end of a calculation.
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.
Unit conversion is simply multiplication by a fixed ratio. The ratio between two units of the same quantity never changes, so once you know it you can convert any value in either direction.
For any value, use the Millibars to PSI Converter or browse all pressure converters.
Run your own numbers: Millibars to PSI Converter