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Bar to Millibar Converter
↔ Convert mbar to bar instead

Common Conversions

bar mbar
0.001 1
0.01 10
0.05 50
0.1 100
0.25 250
0.5 500
1 1000
2 2000
5 5000
10 10000
50 50000
100 100000

Why this conversion matters in chemistry

Solvent vapor-pressure tables and reactor ratings live in bar; rotary-evaporator controllers, freeze-dryer setpoints, and most vacuum gauges read in millibar. The factor between them is exactly 1000. A 0.150 bar setpoint for ethanol removal at 40 °C reads as 150 mbar on the rotavap controller — the unit with mbar resolution that's better matched to the 10–500 mbar working range of solvent distillation than whole-bar steps would be.

Formula

mbar = bar × 1000

Worked Examples

1 bar = 1000 mbar

The IUPAC standard pressure expressed at the mbar scale most gauges actually read.

1.01325 bar = 1013.25 mbar

One standard atmosphere — the sea-level baseline for any barometric work.

0.5 bar = 500 mbar

Half-bar reduced pressure, in the working range of vacuum distillation for moderately volatile solvents.

2 bar = 2000 mbar

About the elevated pressure inside a moderately pressurized reactor or autoclave.

Frequently Asked Questions

How do I convert bar to millibar?
Multiply by 1000. The relationship is exact, so 1 bar is precisely 1000 mbar with no rounding.
When does each unit make sense?
Millibar fits small pressure differences and vacuum measurements (0–1013 mbar range), where the finer resolution of the unit matters. Bar takes over for higher pressures — compressed gases, hydrogenation reactors, and IUPAC standard-state thermodynamic references.
Is bar an SI unit?
Not officially, but it's accepted for use alongside SI. 1 bar equals exactly 100,000 Pa or 100 kPa. Since 1982, IUPAC has used 1 bar as the standard pressure for tabulated thermodynamic data.