# why

Discussion in 'Earth Science' started by sculptor, Apr 2, 2021.

1. ### sculptorValued Senior Member

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8,335
why
do some people call a millibar a hectopascal?

and
which word do you use?

...........................................
(I ain't completely confused yet----but I am working on it.)

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3. ### RainbowSingularityValued Senior Member

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milli is old system ?
hecto is new system ?

https://en.wikipedia.org/wiki/Bar_(unit)

https://en.wikipedia.org/wiki/Pascal_(unit)

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5. ### exchemistValued Senior Member

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The Pascal is the SI unit. The bar (1 bar = 10⁵ Pascals) is a non-SI metric unit.

So yes, 1 millibar = 100 Pascals.

I tend to think in terms of bar, but I'm old-fashioned. If you are taking a school examination in Europe, you need to use SI units or you lose marks.

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7. ### sculptorValued Senior Member

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I prefer millibars----(it's more comfortable to say than hectopascal)
and it's on my barometer
as is cm/hg
meanwhile the local meteorologists use inches of mercury

8. ### James RJust this guy, you know?Staff Member

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37,764
I guess the motivation for measuring pressure in bars is that the air pressure at sea level hovers near 1 bar.

For more accuracy, we can use millibars, which means weather reporters can talk about "pressure of 1013 millibars" rather than "1.013 bars".

But the standard SI unit of pressure is the Pascal, and 1 millibar is the same as 1 hectopascal. "Hecto-" is a standard SI prefix that means "one hundred". So, "1013 millibars" is the same as "1013 hecto-Pascals".