The bar (symbol: bar) is a metric unit of pressure defined as exactly 100,000 pascals. It is widely used in meteorology, automotive tire specifications, and industrial processes where the metric system is standard.
The pound per square inch (abbreviated psi) belongs to the Imperial system and represents the pressure exerted by one pound-force applied to an area of one square inch. PSI is common in the United States for tire pressure, hydraulic systems, and engineering specifications.
Both units measure the same physical quantity—force per unit area—but they belong to different measurement systems. Converting between them is essential when working on international projects or interpreting data from sources that use different standards.
Bar to Pound per square inch Conversion Reference Table
Bar (bar)
Pound per square inch (psi)
0.1
1.4504
0.5
7.2519
1.0
14.5038
2.0
29.0075
5.0
72.5189
10.0
145.0377
20.0
290.0755
50.0
725.1887
100.0
1450.3774
500.0
7251.8872
1000.0
14503.7744
Step‑by‑Step Conversion Example
Convert 10 bar to psi.
Write down the known conversion factor: \(1\,\text{bar}=14.503774389728312\,\text{psi}\).
Multiply the value in bar by the factor.
\$\$\n 10\,\text{bar}\times\frac{14.503774389728312\,\text{psi}}{1\,\text{bar}}\;=\;145.03774389728312\,\text{psi}
\$\$
Round to a sensible number of significant figures (e.g., 145 psi).
Therefore, 10 bar ≈ 145 psi.
The bar is convenient because it is close to atmospheric pressure (≈1 bar) and uses a round number (100 kPa). This makes mental calculations and engineering specifications easier, especially in fields that historically adopted the bar before the pascal became widespread.
The factor is exact because 1 bar is defined as exactly 100 000 Pa and 1 psi is defined as exactly 6894.757293168361 Pa. Dividing the two exact values yields the precise conversion constant shown above.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)