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To convert from millimeter of mercury (mmHg) to Inch of mercury (inHg), use the following formula:
With is the ratio between the base units kilopound per square inch (ksi) and kilopascal (kPa).
Let's convert 5 millimeter of mercury (mmHg) to Inch of mercury (inHg).
Using the formula:
Therefore, 5 millimeter of mercury (mmHg) is equal to Inch of mercury (inHg).
Here are some quick reference conversions from millimeter of mercury (mmHg) to Inch of mercury (inHg):
| millimeters of mercury | Inches of mercury |
|---|---|
| 0.000001 mmHg | inHg |
| 0.001 mmHg | inHg |
| 0.1 mmHg | inHg |
| 1 mmHg | inHg |
| 2 mmHg | inHg |
| 3 mmHg | inHg |
| 4 mmHg | inHg |
| 5 mmHg | inHg |
| 6 mmHg | inHg |
| 7 mmHg | inHg |
| 8 mmHg | inHg |
| 9 mmHg | inHg |
| 10 mmHg | inHg |
| 20 mmHg | inHg |
| 30 mmHg | inHg |
| 40 mmHg | inHg |
| 50 mmHg | inHg |
| 100 mmHg | inHg |
| 1000 mmHg | inHg |
| 10000 mmHg | inHg |
For all Pressure converters, choose units using the From/To dropdowns above.
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:
An inch of mercury, often abbreviated as inHg, is a unit of pressure.
It is not part of the standard metric (SI) system but is widely used in the United States and in specific fields like meteorology and aviation.
The unit is defined by its name: it is the amount of pressure exerted by a column of liquid mercury exactly one inch tall at a standard temperature.
You will most commonly encounter inches of mercury in a few key areas:
Weather Reporting: In the U.S., inHg is the standard unit for reporting barometric pressure (also known as atmospheric pressure).
A "high" pressure system indicating clear weather might be around 30.50 inHg, while a "low" pressure system associated with storms could be 28.50 inHg.
Aviation: This measurement is critical for pilot safety.
Pilots use the local barometric pressure (in inHg) to calibrate their altimeters—instruments that measure altitude—to ensure they are flying at the correct height.
Vacuum Systems: The unit is also widely used in science and industry to measure vacuum pressure.
This is common in systems like air conditioning, refrigeration, and for monitoring the manifold pressure in piston engines.
Because inHg is not a global standard, it's often necessary to convert it to other pressure units for calculations or international use.
Here are the most common conversions for 1 inHg: