Pounds per square inch.
PSI to Millibars Converter — psi to mbar
Convert PSI (psi) to Millibar (mbar) using the exact conversion factor (1 psi = 68.94757293 millibar). See the formula, worked examples, conversion table, history, and common uses.
PSI to Millibars 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.
A millibar is 100 pascals.
Result = input x 6894.757293 / 100.
Pressure uses the pascal as the base unit.
Reserved above the conversion cards and below the converter.
About Converting PSI to Millibars
PSI and Millibar 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. PSI is most often used for tire pressure specifications in the us.
Formula
millibars = psi × 68.9475729317
This factor comes from each unit's defined relationship to the category's base unit: 1 psi equals 6894.75729317 base units, and 1 millibar equals 100 base units, so dividing one by the other gives the direct psi-to-millibar factor of 68.9475729317.
Simple example
1 psi × 68.94757293 = 68.94757293 mbar
1 psi = 68.94757293 millibars.
Real-world example
35 psi × 68.94757293 = 2,413.165053 mbar
35 psi = 2,413.165053 millibars.
Conversion table
| PSI (psi) | Millibar (mbar) |
|---|---|
| 1 psi | 68.94757293 mbar |
| 5 psi | 344.7378647 mbar |
| 10 psi | 689.4757293 mbar |
| 25 psi | 1,723.689323 mbar |
| 50 psi | 3,447.378647 mbar |
| 100 psi | 6,894.757293 mbar |
Reverse conversion: Millibar to PSI
68.94757293 mbar × 0.01450377377 = 1 psi
68.94757293 millibars = 1 psi.
psi = millibars × 0.014503773773
For a page dedicated to this direction, see Millibar to PSI.
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.
Understanding the Millibar (mbar)
A millibar is 100 pascals.
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 millibars are in 1 psi?
1 psi equals 68.94757293 millibars, using the exact defined conversion factor rather than an estimate.
How do I convert psi to millibar?
Multiply the psi value by 68.94757293. The converter above does this instantly to whatever precision you set.
How do I convert millibar back to psi?
Use the reverse factor: 1 millibar equals 0.0145037738 psi. You can also use the swap control in the converter above to flip the direction instantly.
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.
What is a millibar?
Millibar (mbar) is a unit of pressure.
Is the psi to millibar 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.
Where is the psi still used today?
United States (standard pressure unit for tires, tools, and plumbing)