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Convert bar to atmospheres (atm) instantly with our free online calculator. Essential for meteorology, industrial pressure systems, scientific research, and engineering applications.
0.986923
Atmospheres per Bar
1.01325
Bar per Atmosphere
~1.3%
Difference Between Units
Formula: Atmospheres = Bar × 0.986923
| Bar | Atmospheres (atm) | Context |
|---|---|---|
| 0.5 bar | 0.4935 atm | Low pressure weather system |
| 0.95 bar | 0.9376 atm | Intense hurricane core |
| 1.0 bar | 0.9869 atm | Standard bar reference |
| 1.013 bar | 1.0000 atm | Sea level atmospheric pressure |
| 1.02 bar | 1.0063 atm | High pressure weather system |
| 1.5 bar | 1.4804 atm | Moderate industrial pressure |
| 2.0 bar | 1.9738 atm | Scuba tank at 20m depth |
| 3.0 bar | 2.9608 atm | Compressed air systems |
| 5.0 bar | 4.9346 atm | Hydraulic brake systems |
| 10 bar | 9.8692 atm | Industrial compressors |
| 200 bar | 197.38 atm | Scuba tank storage pressure |
| 300 bar | 296.08 atm | High-pressure diving tank |
A bar is a metric unit of pressure equal to exactly 100,000 pascals (or 100 kilopascals). Introduced in 1909 by British meteorologist William Napier Shaw, the bar derives its name from the Greek word baros, meaning weight. One bar is approximately equal to atmospheric pressure at sea level (within 1.3%), which makes it a practical unit for engineering, meteorology, and industrial applications. The bar is not part of the International System of Units (SI) but is accepted for use alongside SI units.
An atmosphere (atm) is a unit of pressure defined as exactly 101,325 pascals. It represents the average atmospheric pressure at sea level at 15°C (59°F). Originally based on physical measurements of Earth's atmosphere, the standard atmosphere is now a precisely defined value used extensively in chemistry, physics, diving medicine, and scientific calculations. The atmosphere is convenient for expressing pressures relative to normal sea-level conditions.
The relationship between these units is: 1 bar = 0.986923 atm, or conversely, 1 atm = 1.01325 bar. These units differ by only about 1.3%, making them nearly interchangeable in casual use. However, precise scientific work, engineering specifications, and safety calculations require exact conversion. Understanding this conversion is essential for meteorologists reading weather maps, engineers working with European equipment specifications, scientists conducting experiments at controlled pressures, and divers calculating tank capacities.
The formula to convert bar to atmospheres is: Atmospheres = Bar × 0.986923. Simply multiply the pressure in bar by the conversion factor 0.986923 to get the equivalent pressure in atmospheres.
Question: A weather station reports 1.013 bar pressure. How many atmospheres is this?
Question: A scuba tank is filled to 200 bar. Convert to atmospheres for dive calculations.
Note: This is a common full-tank pressure for recreational scuba diving.
Question: An industrial air compressor operates at 5 bar. What is this in atmospheres?
For a quick estimate, remember that bar and atm are almost equal (within 1.3%). For rough calculations, you can treat them as equivalent: 1 bar ≈ 1 atm. For slightly better accuracy, multiply bar by 0.987 or simply subtract 1.3% from the bar value. For example: 100 bar × 0.987 = 98.7 atm (exact: 98.69). This mental trick works well for quick sanity checks and field estimates.
| Condition | Bar | Atmospheres |
|---|---|---|
| Record low (Typhoon Tip, 1979) | 0.870 | 0.8586 |
| Category 5 hurricane | 0.920 | 0.9080 |
| Strong low pressure | 0.980 | 0.9672 |
| Standard sea level | 1.013 | 1.0000 |
| High pressure system | 1.040 | 1.0264 |
| Record high (Siberia, 1968) | 1.084 | 1.0698 |
| Depth/Application | Bar | Atmospheres |
|---|---|---|
| Surface (sea level) | 1.0 | 0.987 |
| 10 meters depth | 2.0 | 1.974 |
| 20 meters depth | 3.0 | 2.961 |
| 30 meters depth | 4.0 | 3.948 |
| Recreational dive limit (40m) | 5.0 | 4.935 |
| Technical diving (60m) | 7.0 | 6.908 |
| Commercial diving (100m) | 11.0 | 10.856 |
| System/Equipment | Bar | Atmospheres |
|---|---|---|
| Car tire (typical) | 2.5 | 2.467 |
| Bike tire (road) | 7.0 | 6.908 |
| Hydraulic brake system | 50 | 49.346 |
| Industrial air tools | 6–8 | 5.92–7.90 |
| Pressure washer | 100–200 | 98.7–197.4 |
| Steam boiler | 10–30 | 9.87–29.61 |
Weather maps worldwide use millibars (1000 mb = 1 bar) to display atmospheric pressure. Converting between bar and atmospheres helps meteorologists, pilots, and weather enthusiasts understand pressure systems, predict weather patterns, and communicate forecasts across international standards.
European equipment specifications use bar, while scientific literature often uses atmospheres. Engineers working with hydraulic systems, compressed air equipment, pressure vessels, and industrial machinery need accurate conversion for safety compliance, equipment specification, and cross-region compatibility.
Chemistry experiments, physics calculations, and materials science research commonly specify reaction conditions in atmospheres. Converting from bar (common on European lab equipment) to atmospheres ensures accurate experimental replication, proper safety protocols, and consistent scientific communication.
Dive computers, tank pressure gauges, and decompression tables use bar, while dive physiology calculations often reference atmospheres. Accurate conversion is critical for calculating safe dive profiles, gas consumption rates, nitrogen absorption, and preventing decompression sickness.
When converting bar to atmospheres, the result will always be slightly smaller (by about 1.3%). If your atm value is larger than the bar value, you made an error.
The factor 0.986923 rounded to 0.9869 provides accuracy within 0.003%, which is sufficient for virtually all engineering and scientific applications.
Weather forecasts use millibars (mb). 1 bar = 1000 mb, so 1013.25 mb (standard pressure) = 1.01325 bar. Always check the units to avoid 1000× errors.
Bar to atm requires multiplication by 0.986923. Dividing by 0.986923 gives atm to bar (the reverse conversion). Mixing these up is a common error.
Barometric pressure is the measured atmospheric pressure (usually around 1 bar). "Bar" is the unit. Saying "the barometric pressure is 2 bar" is fine, but calling a 5-bar tire pressure "barometric" is incorrect.
While 1 bar ≈ 1 atm works for rough estimates, diving decompression tables, pressure vessel ratings, and chemical reactions require precise values. Use at least 4 decimal places for safety-critical work.
1 bar equals 0.986923 atmospheres, or approximately 0.987 atm. Conversely, 1 atmosphere equals 1.01325 bar. These units are nearly identical, differing by only about 1.3%, which is why they are often used interchangeably in casual contexts, though precise scientific work requires exact conversion.
Bar was intentionally defined to be close to atmospheric pressure for convenience. One bar (100,000 Pa) is slightly less than one atmosphere (101,325 Pa), making conversions relatively simple. This near-equivalence makes bar a practical unit for applications where atmospheric pressure is a reference point.
1 atmosphere is larger than 1 bar by about 1.3%. Specifically, 1 atm = 1.01325 bar. This means at standard sea-level conditions (1 atm), a pressure gauge calibrated in bar would read approximately 1.013 bar.
Use bar for engineering applications, European equipment specifications, and when working with metric SI units. Use atmospheres for scientific calculations, chemistry, and when discussing pressure relative to Earth's atmosphere. Both are acceptable; the choice often depends on industry standards and regional preferences.
A bar is a metric unit of pressure equal to exactly 100,000 pascals or 100 kilopascals (kPa). It was introduced in 1909 and derives its name from the Greek word 'baros' meaning weight. One bar is approximately equal to atmospheric pressure at sea level, making it practical for engineering, meteorology, and industrial applications.
An atmosphere (atm) is a unit of pressure defined as exactly 101,325 pascals. It represents the average atmospheric pressure at sea level at 15°C. Originally based on physical measurements of Earth's atmosphere, it is now a defined standard used extensively in chemistry, physics, and scientific calculations.
To convert bar to atmospheres, multiply the bar value by 0.986923. For example: 5 bar × 0.986923 = 4.934615 atm. For a quick mental estimate, you can use 0.987 as the conversion factor, which gives results accurate to within 0.01%.
Bar is commonly used in meteorology (as millibars for weather forecasting), scuba diving (tank pressure ratings), hydraulic systems, automotive (tire pressure in Europe), industrial compressed air systems, and HVAC engineering. European engineering specifications predominantly use bar rather than PSI.
This calculator uses the internationally recognized conversion factor of 1 bar = 0.986923 atm (derived from 1 atm = 101,325 Pa and 1 bar = 100,000 Pa). For safety-critical applications, pressure vessel design, diving decompression calculations, and regulatory compliance, always verify conversions with certified instruments and consult relevant industry standards.