vacuum range pressure in hpa (mbar) molecules / cm 3 molecules / m 3  mean free path
0   ambient pressure                   1013        2.7 10 19       2.7 10 25           68 nm
1         low vacuum                300 - 1    10 19 - 10 16   10 25 - 10 22    0.1 - 100 μm
2      medium vacuum               1 - 10 3    10 16 - 10 13   10 22 - 10 19    0.1 - 100 mm
3        high vacuum            10 3 - 10 7     10 13 - 10 9   10 19 - 10 15    10 cm - 1 km
4  ultra high vacuum           10 7 - 10 12      10 9 - 10 4   10 15 - 10 10  1 km - 10 5 km

Table as JSON:
{"vacuum range":{"0":"ambient pressure","1":"low vacuum","2":"medium vacuum","3":"high vacuum","4":"ultra high vacuum"},"pressure in hpa (mbar)":{"0":"1013","1":"300 - 1","2":"1 - 10 3","3":"10 3 - 10 7","4":"10 7 - 10 12"},"molecules \/ cm 3":{"0":"2.7 10 19","1":"10 19 - 10 16","2":"10 16 - 10 13","3":"10 13 - 10 9","4":"10 9 - 10 4"},"molecules \/ m 3":{"0":"2.7 10 25","1":"10 25 - 10 22","2":"10 22 - 10 19","3":"10 19 - 10 15","4":"10 15 - 10 10"},"mean free path":{"0":"68 nm","1":"0.1 - 100 μm","2":"0.1 - 100 mm","3":"10 cm - 1 km","4":"1 km - 10 5 km"}}