General
Bar to ATM Conversion Calculator
Convert pressure measurements between bar and atmospheres (ATM) quickly and accurately.
Reviewed by the calculator.uk.com Team · Last reviewed 5 August 2026 · Our methodology
Enter a value in either Bar or ATM to see the conversion result
Related to Bar to ATM Conversion Calculator
The Bar to ATM Conversion Calculator provides a simple and accurate way to convert pressure measurements between bar and standard atmospheres (ATM). The calculator uses precise conversion factors based on the international standard for pressure units:
Conversion Formulas
• 1 bar = 0.986923 atm
• 1 atm = 1.01325 bar
These conversion factors are derived from the standard atmospheric pressure at sea level, which is defined as exactly 101,325 pascals (Pa). Both bar and ATM are commonly used pressure units in various scientific and engineering applications, making this conversion tool essential for professionals and students working with pressure measurements.
The calculator displays results in both bar and ATM units with six decimal places for high precision. This level of precision is important in many scientific and engineering applications where accurate pressure measurements are crucial.
Understanding the Units
• Bar (bar): A metric unit of pressure equal to 100,000 pascals
• Standard Atmosphere (ATM): The average pressure at sea level, equal to 101,325 pascals
The results can be easily copied to clipboard for use in reports, calculations, or other applications. The conversion is instantaneous and bidirectional - you can enter either bar or ATM values to get the corresponding conversion.
1. Why do we use both bar and ATM units?
Bar is commonly used in engineering and industrial applications, while ATM is often used in physics and chemistry. Having both units allows for easy comparison and conversion between different fields and applications.
2. Is bar exactly equal to one atmosphere?
No, 1 bar is slightly different from 1 atmosphere. One bar equals 0.986923 ATM, or approximately 98.69% of one standard atmosphere.
3. Which unit is more commonly used in industry?
Bar is more commonly used in industrial applications, particularly in Europe and in pressure gauge measurements. ATM is more frequently used in theoretical calculations and academic settings.
4. How accurate are the conversions?
The conversions are accurate to six decimal places, using the internationally accepted conversion factors. This level of precision is sufficient for most scientific and engineering applications.
5. What is the scientific source for this calculator?
A bar is defined as exactly 100,000 pascals, while the standard atmosphere is defined as exactly 101,325 pascals, two separate metric reference pressures that happen to be close but not identical, which is why 1 bar works out to about 0.98692 atm rather than a round number. Both definitions come from international metrology agreements rather than physical measurement, so the ratio between them is exact.