Bar to Atm Converter
Convert pressure units between bar and standard atmosphere (atm) with precision
Pressure Conversion
Conversion Result
Popular Bar to Atm Conversions
These commonly referenced pressure conversions are frequently needed in scientific, engineering, and industrial applications.
| Bar (bar) | Standard Atmosphere (atm) |
|---|---|
| 0.1 bar | 0.0987 atm |
| 0.5 bar | 0.4935 atm |
| 1 bar | 0.9869 atm |
| 1.5 bar | 1.4804 atm |
| 2 bar | 1.9738 atm |
| 3 bar | 2.9608 atm |
| 5 bar | 4.9346 atm |
| 10 bar | 9.8692 atm |
| 15 bar | 14.8038 atm |
| 20 bar | 19.7385 atm |
| 25 bar | 24.6731 atm |
| 50 bar | 49.3462 atm |
| 100 bar | 98.6923 atm |
Atmosphere to Bar Conversion Table
| Standard Atmosphere (atm) | Bar (bar) |
|---|---|
| 0.1 atm | 0.1013 bar |
| 0.5 atm | 0.5066 bar |
| 1 atm | 1.0133 bar |
| 2 atm | 2.0265 bar |
| 3 atm | 3.0398 bar |
| 5 atm | 5.0663 bar |
| 10 atm | 10.1325 bar |
| 15 atm | 15.1988 bar |
| 20 atm | 20.2650 bar |
| 50 atm | 50.6625 bar |
| 100 atm | 101.3250 bar |
Conversion Formulas
Bar to Atm Formula
Multiply the pressure value in bar by 0.986923 to obtain the equivalent value in standard atmospheres.
Step-by-Step Conversion Process:
- Identify the pressure value you have in bar
- Multiply that value by the conversion factor 0.986923
- The result represents the equivalent pressure in standard atmospheres (atm)
- Round to the appropriate number of decimal places for your application
5 bar × 0.986923 = 4.9346 atm
20 bar × 0.986923 = 19.7385 atm
Atm to Bar Formula
Multiply the pressure value in standard atmospheres by 1.01325 to obtain the equivalent value in bar.
Step-by-Step Conversion Process:
- Identify the pressure value you have in standard atmospheres (atm)
- Multiply that value by the conversion factor 1.01325
- The result represents the equivalent pressure in bar
- Round to the appropriate number of decimal places as needed
3 atm × 1.01325 = 3.0398 bar
10 atm × 1.01325 = 10.1325 bar
Units Explained
What is a Bar?
The bar is a metric unit of pressure defined as exactly 100,000 pascals (Pa) or 100 kilopascals (kPa). It was introduced as a more convenient alternative to the pascal for expressing atmospheric pressures and is widely adopted in meteorology, engineering, and manufacturing sectors. The bar approximates the atmospheric pressure on Earth at sea level, making it an intuitive reference point for many applications.
What is a Standard Atmosphere (atm)?
The standard atmosphere (atm) represents the average atmospheric pressure at mean sea level in the International Standard Atmosphere model. It is precisely defined as 101,325 pascals (Pa) or 1.01325 bar. This unit originated from early barometric measurements and remains the standard reference pressure in chemistry, physics, and many scientific disciplines. One atmosphere corresponds to the pressure exerted by a 760 mm column of mercury at 0°C under standard gravity.
1 Bar
1 Atmosphere
Why Two Different Units?
Whilst bar and atm measure the same physical quantity (pressure), they serve different purposes. The bar emerged from the metric system to provide a clean, decimal-based unit convenient for engineering and industrial applications. The standard atmosphere, conversely, has historical roots in atmospheric science and provides a natural reference point for Earth’s atmospheric pressure. The 1.3% difference between them means that for many everyday applications, they can be considered nearly equivalent, but precision work requires proper conversion.
Common Applications
Industrial Pressure Systems
Manufacturing facilities frequently specify hydraulic and pneumatic system pressures in bar, whilst safety standards and regulatory documents often reference standard atmospheres. Operators must convert between these units to ensure compliance with equipment specifications and safety protocols.
Meteorology and Weather Science
Weather forecasting traditionally expresses atmospheric pressure in millibars (mb) or hectopascals (hPa), which are equivalent. However, when comparing to standard atmospheric conditions or conducting scientific analysis, meteorologists convert to standard atmospheres to establish deviations from normal pressure.
Diving and Underwater Activities
Scuba divers encounter pressure measurements in both bar and atm when planning dives and managing compressed air supplies. Dive computers and pressure gauges may display readings in bar, whilst decompression tables and physiological calculations often reference atmospheres absolute (ATA), where 1 ATA equals 1 atm.
Laboratory and Scientific Research
Chemistry laboratories conduct experiments under controlled pressure conditions, with many reference materials citing standard atmosphere as the baseline. Laboratory equipment such as autoclaves, reactors, and gas cylinders may measure pressure in bar, necessitating conversion for accurate experimental protocols.
Automotive Tyre Pressure
Whilst vehicle tyre pressures in the UK are typically specified in psi (pounds per square inch), European specifications often list bar. Some technical documents reference atmospheric pressure when discussing gauge versus absolute pressure measurements, requiring conversion between bar and atm.
Frequently Asked Questions
What is the difference between bar and atm?
The bar is a metric unit equal to 100,000 pascals, whilst the standard atmosphere equals 101,325 pascals. One atmosphere is approximately 1.3% greater than one bar. In practical terms: 1 atm = 1.01325 bar and 1 bar = 0.9869 atm. Both units measure pressure, but atm has historical roots in atmospheric science, whereas bar was designed as a convenient metric unit.
How do you convert 2 bar to atm?
To convert 2 bar to atmospheres, multiply by 0.986923: 2 × 0.986923 = 1.9738 atm. Therefore, 2 bar equals approximately 1.97 standard atmospheres. This conversion is straightforward and applies to any bar value—simply multiply by the conversion factor.
Is 1 bar the same as 1 atmosphere?
No, 1 bar and 1 atmosphere are very close but not identical. One standard atmosphere equals 1.01325 bar, meaning the atmosphere is slightly higher pressure. For rough estimates, they’re often considered equivalent, but precision applications require the exact conversion factor. The difference represents about 1,325 pascals.
Which pressure unit is more commonly used in the UK?
Both bar and psi (pounds per square inch) see widespread use in the UK, with bar being more prevalent in European-standard equipment and engineering contexts. Standard atmospheres appear primarily in scientific literature, chemistry, and academic settings. For tyre pressure and some consumer applications, psi remains common despite metrication efforts.
How do you convert atm to bar?
Multiply the atm value by 1.01325 to obtain bar. For example, 5 atm × 1.01325 = 5.0663 bar. This reverse conversion uses the reciprocal relationship between the units, and the formula works for any positive pressure value.
What is gauge pressure versus absolute pressure?
Gauge pressure measures pressure relative to atmospheric pressure (reading zero at ambient conditions), whilst absolute pressure measures relative to a perfect vacuum. When specifications state “bar” or “atm” without qualification, they typically refer to absolute pressure. However, “barg” explicitly indicates gauge pressure in bar, and many pressure instruments display gauge readings that must be corrected by adding one atmosphere to obtain absolute pressure.
Can I use bar and atm interchangeably?
For approximate calculations or when precision isn’t critical, treating bar and atm as equivalent introduces only minor error. However, for engineering specifications, scientific experiments, safety-critical systems, or any application requiring accuracy better than 2%, you must perform proper conversion. The 1.3% difference can significantly impact outcomes in pressure-sensitive processes.
What is the relationship between bar, atm, and pascal?
The pascal (Pa) is the SI base unit of pressure. Both bar and atm are derived units defined in terms of pascals: 1 bar = 100,000 Pa (or 100 kPa), and 1 atm = 101,325 Pa (or 101.325 kPa). This means you can convert between any of these units through their pascal equivalents.