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mmHg to Bar Converter
↔ Convert bar to mmHg instead

Common Conversions

mmHg bar
1 0.001333
10 0.01333
50 0.06666
100 0.13332
200 0.26664
400 0.53329
500 0.66661
600 0.79993
700 0.93326
750.062 1
760 1.01325
1000 1.33322

Why this conversion matters in chemistry

The bar is the pressure unit IUPAC picked when it wanted standard states in round SI-compatible numbers — 1 bar is exactly 100 kPa, which is a hair below atmospheric. Mercury-column units survive because manometers and vapor-pressure tables predate the switch. Water's vapor pressure at 25 °C is 23.8 mmHg, or about 0.0317 bar; the reduced pressure pulled by a rotary evaporator might be 100 mmHg, or 0.133 bar. Multiplying by 0.001333224 is the bridge between the two worlds — the instrument reading and the standard-state value a thermodynamic data compilation will report.

Formula

bar = mmHg × 0.001333224

Worked Examples

760 mmHg = 1.01325 bar

Standard atmospheric pressure, the sea-level baseline for anything that isn't under vacuum.

750.062 mmHg = 1 bar

Exactly 1 bar — the IUPAC standard pressure, useful for pinning down the right pressure to use in a thermodynamic calculation.

23.8 mmHg = 0.03173 bar

The vapor pressure of water at 25 °C — a number that comes up any time a gas is collected over water.

100 mmHg = 0.13332 bar

A reduced pressure in the range a vacuum filter or a gentle rotavap run would hold.

Frequently Asked Questions

How do I convert mmHg to bar?
Multiply by 0.001333224. So 760 mmHg becomes 1.01325 bar, which is also exactly 1 standard atmosphere.
What's 760 mmHg in bar?
Exactly 1.01325 bar — that's the defined relationship between the standard atmosphere and the bar, and it's the conversion you keep reaching for when moving between textbook atm values and IUPAC-standard bar.
Why bother converting mmHg to bar?
Since 1982, IUPAC has used 1 bar (100 kPa) as the reference pressure for tabulated standard thermodynamic properties. Any calculation anchored to those tables needs the input pressure in bar, which is why mercury-manometer readings have to convert before they enter the algebra.
Is bar an SI unit?
No — the SI unit of pressure is the pascal. Bar is accepted for use alongside SI because 1 bar = 100,000 Pa = 100 kPa, so the conversion to and from the SI unit is a simple decimal shift.