Divide by 760
atm = torr ÷ 760, torr = atm × 760
One atmosphere is defined as exactly 760 torr, so the conversion is a straight divide. The 760 comes from Torricelli's barometer, where sea-level air pressure holds up a 760 mm column of mercury. That definition is exact and temperature-independent.
Quick reference
| Torr | Atmospheres | Pascals | psi |
|---|---|---|---|
| 1 | 0.001316 | 133.3 | 0.01934 |
| 10 | 0.01316 | 1,333 | 0.1934 |
| 100 | 0.1316 | 13,332 | 1.934 |
| 380 | 0.5 | 50,663 | 7.348 |
| 760 | 1.0 | 101,325 | 14.696 |
| 1520 | 2.0 | 202,650 | 29.39 |
380 torr is exactly half an atmosphere — a useful landmark for vacuum work.
Torr, mmHg and the units around them
- Torr vs mmHg. Defined differently but equal to about one part in seven million. Use torr for precise scientific work; mmHg stays standard in medicine and blood pressure.
- Pascals. 1 torr = 133.322 Pa. The pascal is the SI unit and preferred in modern publications, but torr is convenient for vacuum ranges.
- Where torr is used. Vacuum systems and semiconductor fabs run from rough vacuum near 1 torr down to ultra-high vacuum below 10⁻⁹ torr.
Common questions
How do I convert torr to atmospheres?
Divide the torr value by 760. So 500 torr is 500 / 760 = 0.658 atm. To go back, multiply atm by 760.
Is 1 torr the same as 1 mmHg?
Almost. They differ by about one part in seven million, because torr is defined as exactly 1/760 atm while mmHg is tied to a real mercury column. For any practical purpose you can treat them as equal.
How many torr is a full atmosphere?
760 torr, by international definition since 1954. That equals 101,325 pascals, or 14.696 psi.
