How this calculator works
The standard atmosphere is exactly 101,325 pascals. Multiplying by this definition changes the unit without changing the physical pressure or its reference. The supporting readouts show kPa and bar so that large pascal counts are easier to check.
Formula
pascals = atmospheres x 101325; atmospheres = pascals / 101325.
Worked example
0.25 atm is exactly 25,331.25 Pa. Conversely, 202,650 Pa is exactly 2 atm.
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Frequently asked questions
How many pascals are in one atmosphere?
Exactly 101,325 Pa, rather than the rounded estimate of 100,000 Pa.
Can a vacuum pressure be zero?
Zero absolute pressure is the limiting value of an ideal vacuum. This calculator accepts zero and positive pressure values.
Should I use atm or kPa in an equation?
Use whichever unit the equation requires. In SI equations, pressure is usually expressed in Pa, with all other quantities in consistent SI units.