A bar is exactly 100,000 pascals.
Bars to Attopascals Converter — bar to aPa
Convert Bar (bar) to Attopascal (aPa) using the exact conversion factor (1 bar = 1e+23 attopascal). See the formula, worked examples, conversion table, history, and common uses.
Bars to Attopascals 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.
Attopascal is 1e-18 pascal units.
Result = input x 100000 / 1e-18.
Pressure uses the pascal as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Bars to Attopascals
Bar and Attopascal 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 most often used for tire pressure specifications outside the us.
Formula
attopascals = bars × 1e+23
This factor comes from each unit's defined relationship to the category's base unit: 1 bar equals 100000 base units, and 1 attopascal equals 1e-18 base units, so dividing one by the other gives the direct bar-to-attopascal factor of 1e+23.
Simple example
1 bar × 1e+23 = 1e+23 aPa
1 bar = 1e+23 attopascals.
Real-world example
35 bar × 1e+23 = 3.5e+24 aPa
35 bars = 3.5e+24 attopascals.
Conversion table
| Bar (bar) | Attopascal (aPa) |
|---|---|
| 1 bar | 1e+23 aPa |
| 5 bar | 5e+23 aPa |
| 10 bar | 1e+24 aPa |
| 25 bar | 2.5e+24 aPa |
| 50 bar | 5e+24 aPa |
| 100 bar | 1e+25 aPa |
Reverse conversion: Attopascal to Bar
1e+23 aPa × 1e-23 = 1 bar
1e+23 attopascals = 1 bar.
bars = attopascals × 1e-23
For a page dedicated to this direction, see Attopascal to 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 Attopascal (aPa)
Attopascal is 1e-18 pascal units.
Bar — sources
- BIPM SI Brochure — Non-SI units accepted for use with SI — Lists the bar among accepted non-SI pressure units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many attopascals are in 1 bar?
1 bar equals 1e+23 attopascals, using the exact defined conversion factor rather than an estimate.
How do I convert bar to attopascal?
Multiply the bar value by 1e+23. The converter above does this instantly to whatever precision you set.
How do I convert attopascal back to bar?
Use the reverse factor: 1 attopascal equals 1e-23 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 attopascal?
Attopascal (aPa) is a unit of pressure.
Is the bar to attopascal conversion exact?
Yes. A bar is defined as exactly 100,000 pascals, close to (but distinct from) one standard atmosphere (101,325 Pa). 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