About the Pascal to Atmosphere Converter
This pascal to atmosphere converter changes a pressure in pascals into standard atmospheres and every other common pressure unit: kilopascals, bar, torr, millimeters of mercury, inches of mercury and psi. Pick any of them as the starting unit to convert the other way, for example atm to Pa or atm to kPa.
It is aimed at chemistry and physics students applying the ideal gas law, lab and vacuum work quoted in torr, weather data in inches of mercury or hectopascals, and engineering specs given in pascals or psi.
The standard atmosphere is defined as exactly 101,325 Pa, and one torr is exactly 1/760 atm. The mmHg and inHg figures use the conventional values for mercury at 0 °C (133.322 Pa and 3,386.39 Pa), which is what barometers and weather services use.
With the default inputs, the atmospheres is 1 atm. Change any value above to recalculate instantly.
How to use the pascal to atmosphere converter
- 1Enter the pressure value.
- 2Choose the unit you are converting from.
- 3Read atmospheres as the main result, with all other units below.
- 4Remember that gauge readings (such as tire pressure) exclude the atmosphere; add 1 atm for absolute pressure.
Formula and method
The pascal is the SI unit of pressure, one newton per square meter. The standard atmosphere is defined as exactly 101,325 Pa, so dividing pascals by 101,325 gives atmospheres. The bar is exactly 100,000 Pa, and the torr is exactly 1/760 of a standard atmosphere (about 133.3224 Pa).
Conventional millimeters of mercury (133.322387 Pa) differ from the torr by less than one part in seven million, so the two are interchangeable in practice. An inch of mercury at 0 °C is 3,386.389 Pa, and a psi is 6,894.757 Pa. The converter turns any input into pascals first, then divides by each unit's size.
- Pa
- Pascal (N/m²)
- atm
- Standard atmosphere (101,325 Pa)
- Torr
- 1/760 atm
- inHg
- Inch of mercury at 0 °C
Worked examples
101,325 Pa is one atmosphere
101,325 ÷ 101,325 = 1 atm by definition, which is 760 Torr, 29.92 inHg and 14.696 psi.
2.5 atm in kPa
2.5 × 101,325 = 253,312.5 Pa, or 253.31 kPa (2.533 bar).
Weather barometer reading of 30.12 inHg
30.12 × 3,386.389 = 101,998 Pa; 101,998 ÷ 101,325 = 1.0066 atm — slightly above standard, typical of fair weather.
Frequently asked questions
How many pascals are in an atmosphere?+
One standard atmosphere is exactly 101,325 pascals, which is 101.325 kPa or 1.01325 bar.
How do I convert Pa to atm?+
Divide pascals by 101,325. For example, 50,000 Pa ÷ 101,325 = 0.4935 atm.
Is torr the same as mmHg?+
Almost. One torr is exactly 1/760 atm (133.3224 Pa), while one conventional mmHg is 133.3224 Pa to five significant figures — they differ by about 0.000014%, so they are used interchangeably.
What is standard pressure in kPa?+
Standard atmospheric pressure is 101.325 kPa. Note that IUPAC's "standard temperature and pressure" (STP) uses 100 kPa (1 bar) instead, so check which one a textbook means.
How many inches of mercury is one atmosphere?+
One atmosphere is about 29.92 inHg. US weather reports give barometric pressure in inches of mercury, typically between 29.5 and 30.5.