Convert Atmospheres to Bar
Atmospheres to bar is the conversion you need when a pressure is quoted in atmospheres but your gauge or spec uses bar. One standard atmosphere is exactly 1.01325 bar — just a hair above one bar — because both units sit close to average sea-level air pressure.
Atmospheres to Bar conversion table
| Atmospheres (atm) | Bar (bar) |
|---|---|
| 1 | 1.01325 |
| 2 | 2.0265 |
| 3 | 3.03975 |
| 5 | 5.06625 |
| 10 | 10.1325 |
| 20 | 20.265 |
| 50 | 50.6625 |
| 100 | 101.325 |
| 500 | 506.625 |
| 1,000 | 1,013.25 |
The formula
To convert atmospheres to bar, multiply the number of atmospheres by 1.01325:
bar = atmospheres × 1.01325
A worked example
Say a reading is 3 atmospheres and you want it in bar:
3 × 1.01325 = 3.03975 bar
So 3 atmospheres is exactly 3.03975 bar.
Why the number is exact
The "atmosphere" here is the standard atmosphere (atm), defined as exactly 101,325 pascals, and the bar is defined as exactly 100,000 pascals. Both are fixed by definition, so one atmosphere is exactly 1.01325 bar — an exact conversion, not a rounded one.
When you'll use it
Reading a pressure quoted in atmospheres against a gauge or datasheet that uses bar — common in diving, engineering, and lab work, where bar is the everyday unit and the atmosphere shows up in older or textbook figures.
Frequently asked questions
How many bar are in one atmosphere?
Exactly 1.01325 bar. One standard atmosphere is exactly 101,325 pascals and one bar is exactly 100,000 pascals, so an atmosphere works out to exactly 1.01325 bar.
Is one atmosphere the same as one bar?
Almost, but not quite. One atmosphere is 1.01325 bar — about 1.3% higher than one bar. They're close enough that people mix them up, but they're two different definitions.
Is the atmospheres to bar conversion exact?
Yes. Both the atmosphere (101,325 Pa) and the bar (100,000 Pa) are defined exactly, so one atmosphere is exactly 1.01325 bar with nothing rounded away.