Bar to Atmospheres Converter
Bar and standard atmosphere (atm) are nearly equivalent units — the difference is only 1.3%. 1 bar = 100,000 Pa = 0.986923 atm, while 1 atm = 101,325 Pa = 1.01325 bar. This close...
Formula
Source: Engineering Toolbox, NIST | Last reviewed: June 8, 2026
Examples
1 bar
= 0.987 atm
1 bar = 0.987 atm
1.01325 bar
= 1 atm
Standard atmospheric pressure
10 bar
= 9.87 atm
200 bar
= 197.4 atm
Typical scuba cylinder pressure (200 bar)
Quick Reference Table
| bar | atm |
|---|---|
| 1 | 0.987 |
| 1.013 | 1 |
| 2 | 1.974 |
| 5 | 4.935 |
| 10 | 9.869 |
| 100 | 98.69 |
| 200 | 197.38 |
Where is this used?
Pressure vessel design: European codes (PED) use bar, while thermodynamic property tables often use atm.
Gas solubility calculations (Henry's Law) where atmospheres is the standard unit.
Frequently Asked Questions
Why are bar and atm so close in value?
The bar was originally defined to approximate atmospheric pressure. 1 bar = 10⁵ Pa, while 1 atm = 101,325 Pa. The 1.3% difference was deliberately chosen to make the bar a convenient round number in SI units.
When should I use atm instead of bar?
Use atm for scientific calculations involving gas laws, chemical thermodynamics, and diving physiology (ATA). Use bar for industrial pressure specifications in Europe and for general engineering work where the 1.3% difference is negligible.
How does this conversion affect diving calculations?
At 10 m depth in seawater, the gauge pressure is ~1 bar, but the absolute pressure is ~2 bar = 1.97 ATA. For decompression calculations, the 1.3% difference between bar and ATA can become significant over multiple dives.
Reviewed for accuracy
· Last reviewed: June 8, 2026
All calculations are for reference only. Always verify with manufacturer data and a qualified engineer for critical applications. Learn about our editorial process.