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Performing a unit conversion between these two measurements is one of the simplest tasks in physics.
Because the Torr is a unit of pressure historically defined to be identical to the millimeter of mercury, the relationship between these two unit symbols (mmHg and Torr) is essentially one-to-one.
The unit is named in honor of Evangelista Torricelli, a renowned Italian physicist and mathematician who invented the barometer. While modern re-definitions have introduced a microscopic difference (where 1 mmHg is technically 0.999997 Torr), for all general applications, you can treat them as equal when you convert mmhg to torr.
For most practical purposes, the mmhg to torr conversion formula is:
Let's say you have a standard atmospheric pressure reading of 760 mmHg and need to express it in Torr.
The value remains the same, making the conversion instant and easy.
How many millimeters of mercury are in one torr? One torr (torr) contains 1.0000027633927831234 millimeters of mercury (mmHg) — the inverse of the factor above. Multiplying by 0.99999723661485319516 takes you from millimeters of mercury to torr; multiplying by 1.0000027633927831234 brings you back.
Put in words: one millimeter of mercury equals 0.99999723661485319516 torr, so the millimeter of mercury is the smaller unit of this pair. Converting between them never changes the amount of pressure being measured — only the size of the unit you count it in.
A millimeter of mercury (mmHg) is a manometric unit of pressure.
It was historically defined as the pressure generated by a column of mercury exactly one millimeter high.
Today, it is most famous as the unit used in medicine for measuring blood pressure. It is also commonly used in meteorology, aviation, and physics to measure atmospheric pressure or vacuum pressure.
The mmHg unit originates from the invention of the barometer by Evangelista Torricelli in 1643.
Torricelli's device measured atmospheric pressure by seeing how high it could support a column of mercury in a tube.
Standard atmospheric pressure was found to support a column approximately 760 mm high, which established 760 mmHg as a standard reference point.
The most well-known application of mmHg is in medicine.
Blood Pressure: Readings are given as two numbers: systolic pressure (when the heart beats) over diastolic pressure (when the heart rests), such as 120/80 mmHg. This is a critical vital sign for human health.
Meteorology: Used for reporting barometric (atmospheric) pressure, which helps in weather forecasting.
Physics & Engineering: Used for measuring vacuum pressures and other low-pressure systems where precision is needed.
While mmHg is common, other pressure units are standard in different fields. Here are the most common conversions:
A torr (Torr) is a unit of pressure.
It is primarily used to measure a vacuum, or pressures much lower than the air pressure we experience every day.
While the modern standard (SI) unit for pressure is the pascal (Pa), the torr is still widely used in many scientific and engineering fields.
For conversion, one torr is equal to about 133.32 pascals.
A much simpler way to think about it is in relation to our atmosphere: one standard atmosphere (atm) is defined as exactly 760 Torr.
The unit is named in honor of Evangelista Torricelli, the 17th-century Italian physicist who invented the mercury barometer.
Because of this, one torr was initially defined as being equal to one millimeter of mercury (mmHg).
This means 1 Torr is the pressure exerted by a column of mercury that is one millimeter high.
As mentioned, the torr's most convenient relationship is with the standard atmosphere (atm).
One standard atmosphere—the average air pressure at sea level—is set at exactly 760 Torr.
This straightforward, whole-number conversion makes the torr a popular choice for anyone working with fractions of atmospheric pressure.
The torr is the primary unit of measurement for high-vacuum and ultra-high-vacuum technology.
Because it is such a small unit (it takes 760 of them to equal one atmosphere), it is ideal for quantifying pressures far below normal air pressure.
You will find the torr used in many advanced scientific and industrial fields, including:
Here are some quick reference conversions from millimeter of mercury (mmHg) to torr (torr):
| millimeters of mercury | torr |
|---|---|
| 0.000001 mmHg | 9.9999723661485319516× 10-7 torr |
| 0.001 mmHg | 0.00099999723661485319516 torr |
| 0.1 mmHg | 0.099999723661485319516 torr |
| 1 mmHg | 0.99999723661485319516 torr |
| 2 mmHg | 1.9999944732297063903 torr |
| 3 mmHg | 2.9999917098445595855 torr |
| 4 mmHg | 3.9999889464594127806 torr |
| 5 mmHg | 4.9999861830742659758 torr |
| 6 mmHg | 5.999983419689119171 torr |
| 7 mmHg | 6.9999806563039723661 torr |
| 8 mmHg | 7.9999778929188255613 torr |
| 9 mmHg | 8.9999751295336787564 torr |
| 10 mmHg | 9.9999723661485319516 torr |
| 20 mmHg | 19.999944732297063903 torr |
| 30 mmHg | 29.999917098445595855 torr |
| 40 mmHg | 39.999889464594127806 torr |
| 50 mmHg | 49.999861830742659758 torr |
| 100 mmHg | 99.999723661485319516 torr |
| 1000 mmHg | 999.99723661485319516 torr |
| 10000 mmHg | 9999.9723661485319516 torr |
Engineering datasheets across Europe write millimeter of mercury to torr several different ways. The calculation is the same in every one of them.
| Language | Written as | Unit names |
|---|---|---|
| French | mmHg en torr | millimètre de mercure → torr |
| Spanish | mmHg a torr | milímetro de mercurio → torr |
| Dutch | mmHg naar torr | millimeter kwikdruk → torr |
| German | mmHg in torr | Millimeter Quecksilbersäule → Torr |
| Polish | mmHg na torr | milimetr słupa rtęci → torr |
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