$1$atm $= 101325$pa
$1$bar $= 100000$ pa
$1$atm $= 1.013$ bar
$1$bar $= 0.987$atm

From wiki:

The bar is a metric (but not SI) unit of pressure exactly equal to $100000$ Pa.[1] It is about equal to the atmospheric pressure on Earth at sea level. Atmospheric pressure is the pressure exerted by the weight of air in the atmosphere.

My question: I presume ground level is higher than sea level. #Why is the pressure at sea level Less than at ground level?# I thought that since sea level is at a lower level, there will be a greater weight of air and hence higher pressure on it compared to at ground level

my correction. I am sorry. Why is the pressure at sea level =1bar Less than at ground level=1atm, when supposedly there would be more air hence a greater weight of air hence a higher pressure?

  • 3
    $\begingroup$ I'm not sure I understand the question - a bar is roughly one atmosphere (standard), which makes it a kind-of useful unit. Where is the ground level vs sea level coming from? $\endgroup$
    – Jon Custer
    Dec 14, 2015 at 19:00
  • 1
    $\begingroup$ @Boomzxc - You are reading too much into that snippet from wikipedia. We happen to like powers of ten, and 100000 is about equal to 101325. That's all there is to it. $\endgroup$ Dec 15, 2015 at 10:27

2 Answers 2


As David has mentioned, you are interpreting too much into the value 101'325 Pa. This is an average pressure which can change quite a lot depending on the weather. E.g. if you are in a low pressure system, the sea level pressure can be far bellow 100'000 Pa, If the local weather is a high pressure system, it will be much higher than 101'325 Pa.

Of course you are right: ground level pressure is usually lower than sea level pressure.


Why is the pressure at sea level greater than at ground level?

Most of the time, sea level is below ground level.

So, most of the time, you're at a higher elevation than sea level, and the column of air above you will weigh less than it does at sea level.

  • $\begingroup$ Then, why is it that the pressure at ground level(101325pa) is greater than that of sea level(100000pa)? $\endgroup$
    – Boomzxc
    Dec 15, 2015 at 5:37

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