PSI to Bar Converter

Relationship Between PSI and Bar

The conversion between pounds per square inch (PSI) and bar is a common pressure unit conversion between imperial and metric systems.

1 PSI = 0.0689476 bar

Therefore,

1 bar = 14.5038 PSI

To convert PSI to bar, we multiply the PSI value by 0.0689476.

For example, 30 PSI equals approximately 2.07 bar, which is a typical car tire pressure.

Quick Reference:
Standard atmospheric pressure is approximately 14.696 PSI or 1.01325 bar at sea level. The bar unit is commonly used in Europe and many other countries for tire pressure, hydraulic systems, and industrial applications, while PSI is predominantly used in the United States.

Pounds per Square Inch (PSI)

What is PSI?

PSI (pounds per square inch) is a unit of pressure in the imperial and US customary systems. It represents the force in pounds-force applied perpendicular to a surface area of one square inch. PSI is the most common pressure unit in the United States for commercial, industrial, and consumer applications.

Historical Background

PSI evolved from the British imperial system and became the standard pressure measurement in the United States and other countries using imperial units. Despite global metrication efforts, PSI remains deeply rooted in American engineering standards, manufacturing specifications, and everyday applications. The unit's widespread use in the US automotive and industrial sectors has made it a de facto international standard for certain applications.

Common Applications

• Automotive: Tire pressure (30-35 PSI cars, 50-80 PSI trucks, 30-40 PSI motorcycles)
• Hydraulics: Construction equipment (2,000-5,000 PSI), hydraulic brakes (1,000-2,000 PSI)
• Pneumatics: Air compressors (90-150 PSI), air tools (90 PSI), spray guns (40-60 PSI)
• Plumbing: Residential water pressure (40-80 PSI), municipal supply (50-100 PSI)
• Pressure Washing: Consumer (1,500-3,000 PSI), commercial (3,000-8,000 PSI)
• Scuba Diving: Compressed air tanks (3,000-4,500 PSI)
• Gas Systems: Natural gas lines (0.25-60 PSI), propane tanks (100-250 PSI)
• Industrial: Boilers (15-300 PSI), steam systems, compressed gas cylinders
• HVAC: Refrigerant systems (50-400 PSI depending on refrigerant type)
• Fire Safety: Fire extinguishers (100-200 PSI), sprinkler systems (7-30 PSI)

PSI Standards

In the United States, PSI is the legal standard for pressure gauges on consumer and industrial equipment. Most American technical specifications, safety standards (OSHA, ANSI), and equipment ratings are published in PSI. Understanding PSI to bar conversion is essential for international trade, equipment import/export, and compliance with global standards.

PSIA, PSIG, and PSID

• PSIA (Absolute): Pressure measured relative to perfect vacuum. Used in scientific calculations and high-altitude applications.
• PSIG (Gauge): Pressure measured relative to atmospheric pressure. Most common in practical applications. A tire gauge reading 32 PSIG means 32 PSI above atmospheric pressure.
• PSID (Differential): Pressure difference between two points. Used in filter systems, flow measurements, and HVAC applications.
• Conversion: PSIA = PSIG + atmospheric pressure (~14.7 PSI at sea level)

Bar

What is a Bar?

The bar is a metric unit of pressure defined as exactly 100,000 pascals (100 kPa) or approximately equal to the atmospheric pressure on Earth at sea level. The bar is not part of the International System of Units (SI), but it is widely accepted and commonly used in Europe and around the world due to its convenient magnitude.

History and Definition

The bar was introduced in 1909 by British meteorologist William Napier Shaw. The name 'bar' comes from the Greek word 'baros,' meaning weight. Originally intended for meteorological use, it quickly gained widespread adoption in various industries. 1 bar = 100,000 Pa = 100 kPa = 0.1 MPa. The millibar (mbar, 1/1000 bar) is commonly used in meteorology and aviation.

Common Uses

• Automotive tire pressure: Most European specifications are in bar (typically 2.0-2.5 bar)
• Weather forecasting: Atmospheric pressure in millibars (standard pressure ~1013 mbar)
• Scuba diving: Cylinder pressures and depth measurements (10 meters depth ≈ 2 bar)
• Hydraulic systems: Industrial and construction equipment pressure ratings
• Compressed air systems: Workshop compressors typically operate at 6-10 bar
• Steam boilers: Low to medium pressure applications (0.5-10 bar)
• Espresso machines: Optimal brewing pressure is 9 bar
• Pressure cookers: Typically operate at 0.7-1.0 bar above atmospheric
• Industrial process control: Manufacturing and chemical processing
• HVAC systems: Refrigerant and system pressures

Advantages of Bar

The bar provides convenient values close to atmospheric pressure, making it intuitive for many applications. It's widely used in Europe, Asia, and most countries outside the United States. The bar is particularly useful for tire pressure specifications, where typical values range from 2-3 bar, which are easy to remember and work with.

PSI to Bar Conversion Table

Common PSI to bar conversions for reference: