Torr to atmospheres (torr to atm) converter

What is a torr to atmospheres converter?

A torr to atmospheres converter is an online tool that translates a pressure value expressed in torr into its equivalent in standard atmospheres (atm), and vice versa. Both units measure the same physical quantity — pressure, the force applied per unit of area. The torr is named after Evangelista Torricelli, the inventor of the mercury barometer, and is very common in vacuum technology and laboratory work. The standard atmosphere approximates average air pressure at sea level and is a natural reference point for the torr, since the two are linked by a simple whole-number relationship.

How it works

The conversion rests on a single exact definition: one standard atmosphere is defined as exactly 760 torr. To convert torr to atmospheres you divide by 760; to convert atmospheres to torr you multiply by 760.

Because the relationship is exact by definition, the converter simply scales your input. Enter a value in either field and the other updates automatically, so you can move from torr to atm or from atm to torr without re-entering anything. Each field also exposes millimetres of mercury (mmHg) and pascals (Pa), which is convenient because one torr is almost exactly one millimetre of mercury.

Formula

To convert torr to atmospheres, divide by 760:

$\text{atm} = \frac{\text{torr}}{760}$

To convert atmospheres back to torr, multiply by 760:

$\text{torr} = \text{atm} \times 760$

Torr to atmospheres conversion table

The table below lists common torr values with their atmosphere equivalents (rounded to five decimal places).

Examples

Example 1: Converting 760 torr to atmospheres

A standard atmosphere is defined as exactly 760 torr, so dividing gives:

$\frac{760 \text{ torr}}{760} = 1 \text{ atm}$

This is the baseline that makes the torr so convenient for pressures near sea level.

Example 2: Converting 1 atmosphere to torr

Going the other way, one standard atmosphere expressed in torr is:

$1 \text{ atm} \times 760 = 760 \text{ torr}$

Example 3: Converting a vacuum reading of 100 torr to atmospheres

A rough vacuum of 100 torr is about one-eighth of an atmosphere:

$\frac{100 \text{ torr}}{760} \approx 0.13158 \text{ atm}$

Notes

• The torr and the standard atmosphere are both non-SI units; the SI unit of pressure is the pascal (Pa).
• 1 atm = 760 torr exactly, and 1 torr = 1/760 atm ≈ 133.322 Pa.
• One torr is almost identical to one millimetre of mercury (mmHg); the two differ by less than one part in seven million, so for practical purposes they are interchangeable.
• The torr is especially common in vacuum systems, where pressures are often reported in torr or millitorr.

Frequently asked questions

How many torr are in 1 atmosphere?

There are exactly 760 torr in one standard atmosphere, by definition.

How do I convert atmospheres to torr?

Multiply the value in atmospheres by 760. For example, 0.5 atm equals 380 torr.

Is 1 torr the same as 1 mmHg?

They are almost exactly equal. One torr is defined as 1/760 of an atmosphere, while one millimetre of mercury is based on the density of mercury; the two agree to better than one part in a million, so they are treated as equal in everyday use.

What is the difference between torr and the SI unit pascal?

The pascal is the SI unit of pressure (one newton per square metre). One torr equals about 133.322 pascals, and one atmosphere equals exactly 101,325 pascals.

Does this converter handle decimals and large numbers?

Yes. You can enter any positive value, including small vacuum readings in fractions of a torr or large multiples of an atmosphere, and the converted result updates instantly.