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mmHg to Pascals Converter
↔ Convert Pa to mmHg instead

Common Conversions

mmHg Pa
1 133.322
5 666.612
10 1333.22
25 3333.06
50 6666.12
100 13332.2
200 26664.5
400 53328.9
500 66661.2
760 101325
1000 133322

Why this conversion matters in chemistry

The multiplier of 133.322 Pa per mmHg comes straight out of the physics of a mercury column: the density of mercury (13,595.1 kg/m³) times standard gravity (9.80665 m/s²) times one millimeter (10⁻³ m). Standard atmospheric pressure works out to 760 mmHg = 101,325 Pa exactly. The conversion is the standard step from a manometer reading or a vapor-pressure table value into the units PV = nRT actually wants when R is in J/(mol·K). Water's vapor pressure at 25 °C, 23.8 mmHg, becomes 3173 Pa for the SI calculation; the mercury-column number and the SI number describe the same pressure.

Formula

Pa = mmHg × 133.322

Worked Examples

760 mmHg = 101325 Pa

Standard atmospheric pressure expressed in SI base units — the calibration anchor for any sea-level pressure conversion.

1 mmHg = 133.322 Pa

The factor itself, written out — useful as a sanity check on a manometer reading.

23.8 mmHg = 3173.06 Pa

The vapor pressure of water at 25 °C — the value that lands on the right-hand side of any calculation involving gas collected over water.

100 mmHg = 13332.2 Pa

A typical reduced-pressure setting on a rotary evaporator running a moderate-boiling solvent.

Frequently Asked Questions

How do I convert mmHg to Pa?
Multiply by 133.322. So 760 mmHg becomes exactly 101,325 Pa — the defined value of one standard atmosphere.
Where does 133.322 come from?
It's the physical pressure that a 1 mm column of mercury exerts at standard gravity. Density of mercury (13,595.1 kg/m³) × g (9.80665 m/s²) × 0.001 m = 133.322 Pa, which is the conversion factor.
When does this conversion come up in chemistry?
Anywhere R = 8.314 J/(mol·K) sits in an equation. PV = nRT only gives an energy in joules with P in Pa and V in m³. Mixing R with mmHg values silently drops the answer by a factor of about 133.
Is 1 mmHg exactly 133.322 Pa?
The conventional mmHg is defined as exactly 133.322387415 Pa, normally rounded to 133.322 for working calculations. The torr, defined as 1/760 of a standard atmosphere, is within one part in 10⁷ of the mmHg — close enough that the two are interchangeable for any practical chemistry.