A bar is exactly 100,000 pascals.
Bars to Atmospheres Converter — bar to atm
Convert Bar (bar) to Atmosphere (atm) using the exact conversion factor (1 bar = 0.9869232667 atmosphere). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Bars to Atmospheres converter
Converter
Pressure Converter
Convert pascals, bars, PSI, atmospheres, mercury columns, water columns, and engineering pressure units.
Context values
Some unit families need one extra value for a physically accurate result.
A standard atmosphere is exactly 101,325 pascals.
Result = input x 100000 / 101325.
Pressure uses the pascal as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Bars to Atmospheres
Bar and Atmosphere both show up on pressure gauges — psi is standard on US tire and tool specifications, while bar is the everyday pressure unit across most of the rest of the world. Bar is typically associated with widely used in Europe and most of the world for tire pressure, weather, and industrial pressure, while Atmosphere is typically associated with widely used internationally in chemistry, meteorology, and diving/aviation contexts alongside the pascal and bar.
Formula
atmospheres = bars × 0.986923266716
This factor comes from each unit's defined relationship to the category's base unit: 1 bar equals 100000 base units, and 1 atmosphere equals 101325 base units, so dividing one by the other gives the direct bar-to-atmosphere factor of 0.986923266716.
Simple example
1 bar × 0.9869232667 = 0.9869232667 atm
1 bar = 0.9869232667 atmospheres.
Real-world example
35 bar × 0.9869232667 = 34.54231434 atm
35 bars = 34.54231434 atmospheres.
Conversion table
| Bar (bar) | Atmosphere (atm) |
|---|---|
| 1 bar | 0.9869232667 atm |
| 5 bar | 4.934616334 atm |
| 10 bar | 9.869232667 atm |
| 25 bar | 24.67308167 atm |
| 50 bar | 49.34616334 atm |
| 100 bar | 98.69232667 atm |
Reverse conversion: Atmosphere to Bar
0.9869232667 atm × 1.01325 = 1 bar
0.9869232667 atmospheres = 1 bars.
bars = atmospheres × 1.01325
For a page dedicated to this direction, see Atmosphere to Bar.
Bar vs. Atmosphere
| Aspect | Bar | Atmosphere |
|---|---|---|
| Family | Non-SI metric unit accepted for use with SI | non-SI unit accepted for use with the SI |
| Typical use | Tire pressure specifications outside the US | Chemistry (standard conditions are often defined at 1 atm) |
| Where it's used | Widely used in Europe and most of the world for tire pressure, weather, and industrial pressure | Widely used internationally in chemistry, meteorology, and diving/aviation contexts alongside the pascal and bar |
Understanding the Bar
Bar (bar) measures pressure. A bar is defined as exactly 100,000 pascals, close to (but distinct from) one standard atmosphere (101,325 Pa). It is classified as a Non-SI metric unit accepted for use with SI.
Where it's used: Widely used in Europe and most of the world for tire pressure, weather, and industrial pressure
Uses of the Bar today
- Tire pressure specifications outside the US
- Meteorology (weather maps commonly use millibars, hPa)
- Industrial and hydraulic pressure ratings in metric-system countries
History of the Bar
The bar was proposed by Norwegian meteorologist Vilhelm Bjerknes around 1906 as a convenient round pressure unit close to atmospheric pressure, derived from the CGS unit system (one bar equals one million dynes per square centimeter).
Though not an SI unit, the bar remains in wide practical use, particularly in meteorology (as the millibar, now more often written as the equivalent hectopascal) and in tire and hydraulic pressure specifications across most of the world.
Historical origin. Bar was not the invention of a single named person; it developed through the process described above.
Understanding the Atmosphere
Atmosphere (atm) measures pressure. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. It is classified as a non-SI unit accepted for use with the SI.
Where it's used: Widely used internationally in chemistry, meteorology, and diving/aviation contexts alongside the pascal and bar
Uses of the Atmosphere today
- Chemistry (standard conditions are often defined at 1 atm)
- Diving and aviation pressure references
- General reference for everyday atmospheric pressure
Bar — sources
- BIPM SI Brochure — Non-SI units accepted for use with SI — Lists the bar among accepted non-SI pressure units.
Atmosphere — sources
- BIPM SI Brochure — Standard atmosphere listed among non-SI units with a fixed exact value in pascals.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many atmospheres are in 1 bar?
1 bar equals 0.9869232667 atmospheres, using the exact defined conversion factor rather than an estimate.
How do I convert bar to atmosphere?
Multiply the bar value by 0.9869232667. The converter above does this instantly to whatever precision you set.
How do I convert atmosphere back to bar?
Use the reverse factor: 1 atmosphere equals 1.01325 bars. You can also use the swap control in the converter above to flip the direction instantly.
What is a bar?
Bar (bar) measures pressure. A bar is defined as exactly 100,000 pascals, close to (but distinct from) one standard atmosphere (101,325 Pa). It is classified as a Non-SI metric unit accepted for use with SI.
What is a atmosphere?
Atmosphere (atm) measures pressure. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. It is classified as a non-SI unit accepted for use with the SI.
Is the bar to atmosphere conversion exact?
Yes. Defined as exactly 101,325 pascals, originally based on the average atmospheric pressure at mean sea level. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Where is the bar still used today?
Widely used in Europe and most of the world for tire pressure, weather, and industrial pressure