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To convert a pressure from millibar (mbar) to bar, divide by 1,000 — that is, multiply by 0.001.
Exact by the meaning of the prefix: a millibar is one thousandth of a bar. Equivalently, since 1 mbar = 1 hPa, this is also the hPa-to-bar conversion.
A weather chart shows a deep low of 960 mbar and a calculation set up in bar needs the value:
| mbar | bar |
|---|---|
| 1 | 0.001 |
| 10 | 0.01 |
| 100 | 0.1 |
| 500 | 0.5 |
| 1,000 | 1 |
| 1,013.25 | 1.01325 |
| 1,050 | 1.05 |
The arithmetic here cannot fail except by decimal slip, so the useful content is the anchor: 1,013.25 mbar = 1.01325 bar = one standard atmosphere, the reference that ties weather-report numbers to engineering ones. Everyday sea-level pressure wobbles a few percent around it, which is why atmospheric values in bar are always 0.9-something or 1.0-something — a weather number converted to bar that comes out as 9.6 or 0.096 has had its decimal point mislaid, and the sanity check takes one second. The same anchor guards vacuum work from the opposite direction: a "millibar-range" process at 5 mbar is 0.005 bar, three decades below atmosphere, and writing it in bar mostly serves to feed formulas that want a consistent unit before conversion to pascals. As with every pressure conversion, gauge, absolute and differential character ride along unchanged — barometric pressures are absolute by nature, and stay absolute in bar.
How many millibar are in one bar? One bar (bar) contains 1000 millibar (mbar) — the inverse of the factor above. Multiplying by 0.001 takes you from millibar to bar; multiplying by 1000 brings you back.
Put in words: one millibar equals 0.001 bar, so the millibar is the smaller unit of this pair. Converting between them never changes the amount of pressure being measured — only the size of the unit you count it in.
A millibar (mbar) is a metric unit used to measure atmospheric pressure.
It's most commonly used in weather forecasting and reporting.
(Technically, one millibar is equal to 0.1 kilopascal, or kPa).
Meteorologists use millibars as the primary unit to measure and report atmospheric pressure.
On weather maps, you'll see lines called isobars, which connect areas of equal pressure, drawn in millibar intervals.
Standard atmospheric pressure at sea level is about 1013 mbar.
This number is a key benchmark for weather conditions:
Yes, for all practical purposes, a millibar (mbar) and a hectopascal (hPa) are the same.
The two units are used interchangeably.
The conversion is simple: 1 mbar = 1 hPa.
While you'll still see millibars in public weather reports (especially in the U.S.), the hectopascal is the preferred SI (International System of Units) unit for global scientific consistency.
A barometer measures barometric pressure—the weight of the air above you—using millibars.
Watching the change in this reading is key to predicting the weather:
The bar is a metric unit of pressure.
It is defined as exactly 100 kilopascals (kPa), or 100,000 Pascals (Pa).
Although it is not an official part of the International System of Units (SI), it is widely accepted for use with the SI. The bar is a popular unit for measuring pressure because it is very close to the average atmospheric pressure on Earth at sea level.
The term "bar" comes from the Greek word βάρος (baros), which means "weight."
The unit was introduced by British meteorologist William Napier Shaw in 1909. It is still widely used in meteorology, oceanography, and engineering.
A common point of confusion is the difference between a bar and a standard atmosphere (atm).
While they are very close in value, they are not the same:
This means 1 bar is approximately equal to 0.987 atm. Because it's so close to atmospheric pressure and is a round number (100 kPa), the bar is a very convenient unit for many applications.
The bar is a versatile unit used to measure pressure in many industrial and everyday contexts.
Common examples include:
Here are some quick reference conversions from millibar (mbar) to bar (bar):
| millibar | bar |
|---|---|
| 0.000001 mbar | 10-9 bar |
| 0.001 mbar | 10-6 bar |
| 0.1 mbar | 10-4 bar |
| 1 mbar | 0.001 bar |
| 2 mbar | 0.002 bar |
| 3 mbar | 0.003 bar |
| 4 mbar | 0.004 bar |
| 5 mbar | 0.005 bar |
| 6 mbar | 0.006 bar |
| 7 mbar | 0.007 bar |
| 8 mbar | 0.008 bar |
| 9 mbar | 0.009 bar |
| 10 mbar | 0.01 bar |
| 20 mbar | 0.02 bar |
| 30 mbar | 0.03 bar |
| 40 mbar | 0.04 bar |
| 50 mbar | 0.05 bar |
| 100 mbar | 0.1 bar |
| 1000 mbar | 1 bar |
| 10000 mbar | 10 bar |
Engineering datasheets across Europe write millibar to bar several different ways. The calculation is the same in every one of them.
| Language | Written as | Unit names |
|---|---|---|
| French | mbar en bar | millibar → bar |
| Spanish | mbar a bar | milibar → bar |
| Dutch | mbar naar bar | millibar → bar |
| German | mbar in bar | Millibar → Bar |
| Polish | mbar na bar | milibar → bar |
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