Bar to ATM Converter

Relationship Between Bar and Atmosphere

The conversion between bar and atmosphere (atm) is a fundamental pressure unit conversion between metric and scientific systems.

1 atm = 1.01325 bar

Therefore,

1 bar = 0.986923 atm

To convert bar to atmosphere, we divide the bar value by 1.01325 (or multiply by 0.986923).

For example, 1 bar equals approximately 0.987 atm, and 1.01325 bar equals exactly 1 atm, which is standard atmospheric pressure at sea level.

Quick Reference:
Standard atmospheric pressure is exactly 1.01325 bar or 1.000 atm at sea level. The bar unit provides convenient values close to atmospheric pressure, while the atmosphere unit is commonly used in scientific, meteorological, and engineering applications as a reference point.

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.

Atmosphere (atm)

What is an Atmosphere?

The atmosphere (symbol: atm) is a unit of pressure defined as exactly 101,325 pascals (101.325 kPa). It represents the standard atmospheric pressure at sea level on Earth. The atmosphere is commonly used in scientific, meteorological, and engineering applications as a reference point for pressure measurements.

History and Definition

The atmosphere was originally defined based on the average atmospheric pressure at sea level. It has been standardized as exactly 101,325 Pa, which is approximately equal to the pressure exerted by a column of mercury 760 mm high at 0°C under standard gravity. 1 atm = 101,325 Pa = 101.325 kPa = 1.01325 bar.

Common Uses

• Scientific research: Standard reference pressure for experiments and calculations
• Meteorology: Atmospheric pressure measurements and weather forecasting
• Engineering: Pressure vessel ratings, hydraulic systems, and fluid dynamics
• Aviation: Altitude pressure calculations and aircraft systems
• Scuba diving: Depth pressure calculations (every 10 meters ≈ 1 atm additional pressure)
• Industrial processes: Vacuum systems, compression systems, and pressure testing
• Medical equipment: Hyperbaric chambers, respiratory systems
• Chemistry: Reaction conditions, gas law calculations
• Physics: Thermodynamics, fluid mechanics, and gas behavior studies
• Standards: Reference pressure for calibration and measurement standards

Standard Atmospheric Pressure

Standard atmospheric pressure is defined as exactly 101,325 Pa (101.325 kPa) at sea level at 15°C. This value is used as a reference point in many scientific and engineering calculations. Understanding the relationship between bar and atmosphere is essential for working with pressure measurements in different unit systems and for scientific calculations involving atmospheric pressure.

Bar to Atmosphere Conversion Table

Common bar to atmosphere conversions for reference: