Skip to main content

Atmospheres to Torr Converter

↔ Convert torr to atm instead

Common Conversions

atm torr
0.0001 0.076
0.001 0.76
0.01 7.6
0.05 38
0.1 76
0.25 190
0.5 380
1 760
1.5 1140
2 1520
5 3800
10 7600

Why this conversion matters in chemistry

Atmospheres are how pressure gets written in a gas-law problem; torr is how it reads on a rotary-evaporator gauge or a Schlenk line. A textbook value of 1 atm is 760 torr by definition — the same number a mercury manometer would show at sea level, which is exactly where the unit came from. The conversion matters when a solvent table recommends running an evaporation at around 58 torr (a low vacuum for toluene at 40 °C) and the method section was written in atm, or when a Clausius-Clapeyron fit wants pressures in atm and the instrument only knows torr.

Formula

torr = atm × 760

Worked Examples

1 atm = 760 torr

Standard atmospheric pressure at sea level — the anchor point of the conversion.

0.001 atm = 0.76 torr

Low vacuum — well below what a water aspirator can reach and into the territory of a membrane or rotary-vane pump.

0.0001 atm = 0.076 torr

Medium vacuum, where Schlenk-line chemistry with a diffusion or rotary-vane pump tends to operate.

0.5 atm = 380 torr

Roughly atmospheric pressure at the summit of a 5500 m peak — half an atmosphere still supports chemistry, just not comfortably.

Frequently Asked Questions

Are torr and mmHg the same?
For every practical chemistry purpose, yes. The two differ by about one part in 10⁷ due to a slightly different definition of the standard gravity term, but no routine calculation has ever been thrown off by that difference.
How many torr are in 1 atm?
Exactly 760 by definition. The relationship dates to the mercury barometer — 1 atm is the pressure that supports a 760 mm column of mercury, and the torr was named after Torricelli, who built that instrument.
Where does the torr unit show up in chemistry?
Vacuum distillations, sublimations, freeze-drying, and air-sensitive chemistry on a Schlenk line or in a glovebox. Vapor-pressure tables also tend to be reported in torr, which is why Clausius-Clapeyron fits usually start out there.
Who was Torricelli?
Evangelista Torricelli (1608–1647) was an Italian physicist and a student of Galileo. He built the first mercury barometer, demonstrated atmospheric pressure, and gave his name to the unit we still use for vacuum work today.