PSI to Millibars Converter
Enter the pressure in psi below to convert it to millibars.
Convert PSI to Millibars
Enter a value in psi (psi) to convert to millibars (mbar).
Pounds per Square Inch to Millibar Conversion Table
Table showing various pounds per square inch measurements converted to millibars. Click any preset value or arrow to load it into the converter.
| PSI (psi) | Millibars (mbar) |
|---|---|
| 1 psi | 68.9475729 mbar |
| 2 psi | 137.8951459 mbar |
| 2.5 psi | 172.3689323 mbar |
| 5 psi | 344.7378647 mbar |
| 10 psi | 689.4757293 mbar |
| 15 psi | 1,034.213594 mbar |
| 20 psi | 1,378.9514586 mbar |
| 25 psi | 1,723.6893233 mbar |
| 30 psi | 2,068.427188 mbar |
| 50 psi | 3,447.3786466 mbar |
How to Convert PSI to Millibars
To convert psi to millibars, multiply the pressure by the following conversion ratio: 68.9475729 millibars/pounds per square inch.
Since one pounds per square inch is equal to 68.9475729 millibars, you can use this simple formula to convert:
The pressure in millibars is equal to the pressure in psi multiplied by 68.9475729.
For example, here's how to convert 5 psi to millibars using the formula above.
How Many Millibars Are in a Pounds per Square Inch?
There are 68.9475729 millibars in a pounds per square inch, which is why we use this value in the formula above.
Our pounds per square inch to millibar calculator automatically converts your pressure measurements with full decimal and scientific precision across US customary, imperial, and SI metric standards.
PSI and millibars are both units used to measure pressure. Keep reading to learn more about each unit.
What Is a Pounds per Square Inch?
A pounds per square inch is a unit of pressure equal to 6,894.7572932 pascals (Pa), the base unit for pressure. Imperial & US pressure unit equal to 1 pound-force per square inch (6.89476 kPa). [1]
The pounds per square inch is classified as a US customary and imperial unit of pressure. PSI can be abbreviated as psi; for example, 1 pounds per square inch can be written as 1 psi.
When working with psi (psi) in formulas or technical specifications, always verify whether your target system uses SI metric, US customary, or British imperial standards.
In practice, psi (psi) are widely used across large-scale industrial, bulk, and macro-level pressure specifications within US customary and imperial workflows, engineering documentation, and technical data sheets.
What Is a Millibar?
A millibar is a unit of pressure equal to 100 pascals (Pa), the base unit for pressure. Meteorological pressure unit equal to 1/1000 of a bar (100 Pa = 1 hPa). [2]
The millibar is classified as a metric and SI-compatible unit of pressure. Millibars can be abbreviated as mbar; for example, 1 millibar can be written as 1 mbar.
In the metric system, "milli" is the standard SI prefix for thousandths, or 10⁻³. This makes the millibar (mbar) a convenient decimal multiple of the bar (100,000 Pa).
In practice, millibars (mbar) are widely used across standard pressure applications within SI metric workflows, engineering documentation, and technical data sheets.
When converting pressure between psi (psi) and millibars (mbar), keep full floating-point precision (1 psi = 68.9475729 mbar; 1 mbar = 0.0145038 psi) during intermediate calculations and round only the final millibar figure to match your instrument tolerance.
More Pounds per Square Inch & Millibar Conversions
Need to calculate in the opposite direction? Use our millibars to psi calculator to switch your starting unit immediately. You can also explore related tools such as converting millibars to psi, converting psi to bars, or converting psi to kilopascals.
Frequently Asked Questions
References
- [1]NIST SP 811 StandardNIST SP 811 (NIST SP 811 App. B.9 (Pressure & Stress))·Pressure Metrology Standard — PSI (psi) to Millibars (mbar)
- [2]NIST CUU SpecificationNIST CUU (Derived SI Unit: Pascal (Pa))·Unit Specifications: Pounds per Square Inch (psi) & Millibar (mbar)
- [3]BIPM ReferenceBIPM (SI Brochure (9th Ed.) — Mechanics)·Conversion Factors & Mathematical Basis (psi to mbar)