A millibar is 100 pascals.
Millibars to PSI Converter — mbar to psi
Convert Millibar (mbar) to PSI (psi) using the exact conversion factor (1 millibar = 0.0145037738 psi). See the formula, worked examples, conversion table, history, and common uses.
Millibars to PSI converter
Converter
Pressure Converter
Convert pascals, bars, PSI, atmospheres, mercury columns, water columns, and engineering pressure units.
Context values
Some unit families need one extra value for a physically accurate result.
Pounds per square inch.
Result = input x 100 / 6894.757293.
Pressure uses the pascal as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Millibars to PSI
Millibar and PSI both show up on pressure gauges — psi is standard on US tire and tool specifications, while bar is the everyday pressure unit across most of the rest of the world. Specifically: A millibar is 100 pascals, and pounds per square inch.
Formula
psi = millibars × 0.014503773773
This factor comes from each unit's defined relationship to the category's base unit: 1 millibar equals 100 base units, and 1 psi equals 6894.75729317 base units, so dividing one by the other gives the direct millibar-to-psi factor of 0.014503773773.
Simple example
1 mbar × 0.01450377377 = 0.0145037738 psi
1 millibar = 0.0145037738 psi.
Real-world example
35 mbar × 0.01450377377 = 0.5076320821 psi
35 millibars = 0.5076320821 psi.
Conversion table
| Millibar (mbar) | PSI (psi) |
|---|---|
| 1 mbar | 0.0145037738 psi |
| 5 mbar | 0.0725188689 psi |
| 10 mbar | 0.1450377377 psi |
| 25 mbar | 0.3625943443 psi |
| 50 mbar | 0.7251886887 psi |
| 100 mbar | 1.450377377 psi |
Reverse conversion: PSI to Millibar
0.0145037738 psi × 68.94757293 = 1.000000002 mbar
0.0145037738 psi = 1.000000002 millibars.
millibars = psi × 68.9475729317
For a page dedicated to this direction, see PSI to Millibar.
Understanding the Millibar (mbar)
A millibar is 100 pascals.
Understanding the PSI
PSI (psi) measures pressure. PSI (pounds-force per square inch) equals exactly 6,894.757293168 pascals. It is classified as a US/imperial customary unit.
Where it's used: United States (standard pressure unit for tires, tools, and plumbing)
Uses of the PSI today
- Tire pressure specifications in the US
- Hydraulic and pneumatic system ratings
- Plumbing, compressed-air tools, and industrial equipment ratings
History of the PSI
PSI is a derived unit from the pound-force and the inch, both themselves standardized through English and later international agreements rather than invented as a pressure unit from scratch.
It became the default pressure unit in US engineering as pound-force and inch-based measurement dominated American industry through the 19th and 20th centuries, and it remains in everyday use for tires and tools even as most other measurements in the US context stay imperial.
Historical origin. PSI was not the invention of a single named person; it developed through the process described above.
PSI — sources
- NIST Special Publication 811 — Guide for the Use of the International System of Units — Documents conversion factors for psi and other US customary pressure units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many psi are in 1 millibar?
1 millibar equals 0.0145037738 psi, using the exact defined conversion factor rather than an estimate.
How do I convert millibar to psi?
Multiply the millibar value by 0.01450377377. The converter above does this instantly to whatever precision you set.
How do I convert psi back to millibar?
Use the reverse factor: 1 psi equals 68.94757293 millibars. You can also use the swap control in the converter above to flip the direction instantly.
What is a millibar?
Millibar (mbar) is a unit of pressure.
What is a psi?
PSI (psi) measures pressure. PSI (pounds-force per square inch) equals exactly 6,894.757293168 pascals. It is classified as a US/imperial customary unit.
Is the millibar to psi conversion exact?
Yes. PSI (pounds-force per square inch) equals exactly 6,894.757293168 pascals. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.