atm - Standard Atmosphere Pressure Unit

Standard Atmosphere is mainly used as a reference value for the average atmospheric pressure at sea level. It is often used to indicate the depth rating for a water resistant watch, but otherwise is rarely used as a unit for measuring pressure. 1 Standard Atmosphere is defined as being exactly equal to 101,325 Pascals.

Since the atmospheric presssure varies with changes in weather and altitude, it is convenient to standardise on a single value so that ratings, measurements and specifications can be compared. In particular 1 Standard Atmosphere is used by the Aviation industry as the reference standard for sea level pressure.

In the table below you will find the equivalent values for 1 atm in other pressure units.

To calculate the number of atmospheres for a pressure value in other units please click on the relevant unit link below.

For converting many readings to or from atmospheres please use our pressure unit calculator.

atm Pressure Conversion Factors

1.01325	bar
14.6959	psi
1013.25	mbar
101325	N/m²
101325	Pa
1013.25	hPa
101.325	kPa
0.101325	MPa
1.03323	kg/cm²
10332.3	mmH2O 4°C (39.2°F)
1033.23	cmH2O 4°C (39.2°F)
10.3323	mH2O 4°C (39.2°F)
406.782	inH2O 4°C (39.2°F)
33.8985	ftH2O 4°C (39.2°F)
760	mmHg 0°C (32°F)
76	cmHg 0°C (32°F)
29.9213	inHg 0°C (32°F)
760	Torr
760000	mTorr
1	atm
1.03323	at
1013250	dyn/cm²
235.135	oz/in²
760000	µHg 0°C (32°F)
0.00656069	tsi (uk, long)
0.00734797	tsi (usa, short)
1.05811	tsf (usa, short)
2116.22	psf
1033.23	g/cm²