The Physics of Pressure: Why We Convert Between PSI and BAR

Pressure measurements are critical in many fields, from inflation values for vehicle tires to scuba diving equipment and heavy industrial hydraulics. Because different regions and industries use different measurement systems, converting between units is essential.

Let's look at the physics of pressure and the relationship between PSI and BAR.

What is Pressure?

In physics, pressure is defined as the force applied perpendicular to the surface of an object per unit area over which that force is distributed:

$$P = \frac{F}{A}$$

Where:

• P: Pressure.
• F: Force.
• A: Area.

PSI vs. BAR: The Two Standards

• PSI (Pounds per Square Inch): An imperial unit measuring the force of one pound-force applied to an area of one square inch. It is the standard pressure measurement in the United States and the UK automotive industry.
• BAR: A metric unit of pressure, defined as exactly 100,000 Pascals (Pa). It is approximately equal to the atmospheric pressure on Earth at sea level (1.01325 bar). It is widely used in Europe and across scientific disciplines.

The Conversion Factor

Because the underlying units differ, translating between them requires a conversion factor:

• 1 BAR = 14.50377 PSI
• 1 PSI = 0.068947 BAR

To convert pressure values for car tires, machinery, or dive tanks, use our Unit Converter to calculate values instantly.