Convert between standard atmospheres (atm) and pascals (Pa) in either direction.
How it works
The standard atmosphere is defined as exactly 101,325 pascals, so 1 atm = 101,325 Pa exactly. Enter a value in either field and the other updates instantly.
What this does not include
This uses the fixed standard-atmosphere reference value, not a live or local barometric pressure reading.
How to use this calculator
- Enter a value in atmospheres or pascals.
- The other field updates automatically.
Why is the pascal the SI unit for pressure?
The pascal is defined directly from the SI base units (one newton per square meter), making it the coherent SI unit for pressure, while the atmosphere is a practical reference value tied to typical sea-level conditions.
Is 101,325 an arbitrary number?
It was chosen to match the historically measured average sea-level atmospheric pressure, then fixed as an exact defined value for consistency in scientific and engineering work.
Where is the pascal too small a unit to be convenient?
For everyday pressures like atmospheric pressure or tire pressure, pascals produce large, unwieldy numbers, which is why kilopascals, atmospheres, or psi are often used instead in practice.
