About

Pressure unit confusion is a common source of error in industrial and scientific applications. The standard atmosphere (atm) is historically based on mean sea-level pressure, while the bar is a metric unit derived from Pascals. While they are close in value-differing by only about 1.3%-this discrepancy is significant in high-pressure hydraulic systems, diving decompression algorithms, and meteorological forecasting.

This tool delivers precision conversion for engineers and technicians who cannot rely on the rough approximation that 1 atm equals 1 bar. It specifically addresses the needs of users dealing with European equipment (Bar) vs. American or Aviation standards (atm), ensuring calibration and safety margins are maintained.

Formulas

The relationship between Atmospheres and Bars is defined by exact physical constants:

1 atm ≡ 101,325 Pa

1 bar ≡ 100,000 Pa

Therefore:

P_(bar) = P_(atm) × 1.01325

Reference Data

Atmospheres (atm)	Bars (bar)	Context
1 atm	1.01325 bar	Standard Sea Level Pressure
2 atm	2.0265 bar	~10m depth in seawater
5 atm	5.06625 bar	Espresso Machine (Pre-infusion)
9 atm	9.11925 bar	Espresso Extraction Pressure
10 atm	10.1325 bar	Industrial Air Compressor
50 atm	50.6625 bar	Scuba Tank (Partial Fill)
200 atm	202.65 bar	Standard SCUBA Tank Pressure
300 atm	303.975 bar	High-Pressure Composite Cylinders

Frequently Asked Questions

No. While they are very close, 1 atmosphere is approximately 1.01325 bar. Treating them as equal results in a 1.3% error, which can be critical in high-precision chemistry or safety valves.

"atm" stands for Standard Atmosphere (101.325 kPa). "at" stands for Technical Atmosphere (kgf/cm²), which equals approximately 0.968 atm. This tool calculates based on the Standard Atmosphere (atm).

Physically, absolute pressure cannot be negative. However, if you are calculating gauge pressure (relative to ambient), negative values are possible (vacuum). This tool converts the numerical value linearly regardless of sign.