Convert Pascals to Atmospheres
Pascals to atmospheres is the conversion you need when a pressure reading is in pascals but you want it as a multiple of everyday air pressure. One pascal is approximately 0.00000986923 atmospheres, so the number comes out very small — but the anchor is exact: a standard atmosphere is defined as exactly 101,325 pascals.
Pascals to Atmospheres conversion table
| Pascals (Pa) | Atmospheres (atm) |
|---|---|
| 1 | 0.00000986923 |
| 2 | 0.0000197385 |
| 3 | 0.0000296077 |
| 5 | 0.0000493462 |
| 10 | 0.0000986923 |
| 20 | 0.000197 |
| 50 | 0.000493 |
| 100 | 0.000987 |
| 500 | 0.004935 |
| 1,000 | 0.009869 |
The formula
To convert pascals to atmospheres, multiply the pressure in pascals by 0.000009869232667160129 (the same as dividing by 101,325):
atmospheres = pascals × 0.000009869232667160129
A worked example
Say you're converting standard sea-level air pressure, 101,325 Pa, into atmospheres:
101,325 Pa = 1 atm
So 101,325 pascals is exactly 1 atmosphere, by the definition of the standard atmosphere.
Why it's an approximation
The standard atmosphere is defined as exactly 101,325 pascals, so going from atmospheres to pascals is exact. Going the other way, though, means dividing 1 by 101,325, which gives approximately 0.000009869232667160129 — a long decimal that you round for everyday use. So the anchor point is exact, but the per-pascal factor is rounded.
When you'll use it
Expressing a pressure as a multiple of normal air pressure, reading chemistry and physics problems where atmospheres are the standard unit, and comparing tank, altitude, or lab pressures against the roughly one atmosphere we live in.
Frequently asked questions
How many pascals are in one atmosphere?
Exactly 101,325 pascals. The standard atmosphere is defined as exactly 101,325 Pa, which is about average air pressure at sea level.
Why is the per-pascal factor such a long, awkward number?
Because you're dividing 1 by 101,325. The atmosphere is defined as an exact number of pascals, but flipping that around to 'atmospheres per pascal' gives approximately 0.00000986923 — a long decimal you round for everyday use.
Is the pascals to atmospheres conversion exact?
The definition is exact — one atmosphere is exactly 101,325 pascals. But the per-pascal factor, approximately 0.00000986923, is rounded because it's one divided by 101,325.