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To convert a pressure from millimeters of mercury (mmHg) to millibars (mbar), multiply by 1.3332.
The factor comes from the definition of the conventional millimeter of mercury as 133.322 Pa, while a millibar is exactly 100 Pa; dividing the two gives 1.33322. The classic anchor holds in this direction too: 760 mmHg — one standard atmosphere — equals 1,013.25 mbar.
A vacuum drying oven is holding 5 mmHg absolute, and the process specification is written in mbar:
For the reverse conversion multiply by 0.75006 (or divide by 1.3332).
| mmHg | mbar |
|---|---|
| 1 | 1.33 |
| 5 | 6.67 |
| 100 | 133.32 |
| 250 | 333.31 |
| 760 | 1,013.25 |
| 1,000 | 1,333.22 |
Outside meteorology, the place these two units constantly meet is vacuum technology. Older vacuum practice — and the entire North American vacuum industry — measures in mmHg and its alias the Torr (for practical purposes 1 Torr = 1 mmHg; they differ only at the ninth decimal). European vacuum equipment, by contrast, is instrumented in mbar: pump curves, gauge displays and leak-detection specs. Freeze dryers, rotary evaporators, degassing chambers and semiconductor load-locks routinely carry documentation in one unit and gauges in the other, making ×1.3332 a daily operation in lab and plant work. A convenient sanity check when working near rough vacuum: values in mbar should always be about a third larger than in mmHg — if your converted number got smaller, you multiplied the wrong way. Medical readers note: blood-pressure values stay in mmHg by convention worldwide; converting them to mbar is practically never done clinically.
How many millimeters of mercury are in one millibar? One millibar (mbar) contains 0.7500637554192106329 millimeters of mercury (mmHg) — the inverse of the factor above. Multiplying by 1.33322 takes you from millimeters of mercury to millibar; multiplying by 0.7500637554192106329 brings you back.
Put in words: one millimeter of mercury equals 1.33322 millibar, so the millimeter of mercury is the larger 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 millibar (mbar) is a metric unit used to measure atmospheric pressure.
It's most commonly used in weather forecasting and reporting.
(Technically, one millibar is equal to 0.1 kilopascal, or kPa).
Meteorologists use millibars as the primary unit to measure and report atmospheric pressure.
On weather maps, you'll see lines called isobars, which connect areas of equal pressure, drawn in millibar intervals.
Standard atmospheric pressure at sea level is about 1013 mbar.
This number is a key benchmark for weather conditions:
Yes, for all practical purposes, a millibar (mbar) and a hectopascal (hPa) are the same.
The two units are used interchangeably.
The conversion is simple: 1 mbar = 1 hPa.
While you'll still see millibars in public weather reports (especially in the U.S.), the hectopascal is the preferred SI (International System of Units) unit for global scientific consistency.
A barometer measures barometric pressure—the weight of the air above you—using millibars.
Watching the change in this reading is key to predicting the weather:
Here are some quick reference conversions from millimeter of mercury (mmHg) to millibar (mbar):
| millimeters of mercury | millibar |
|---|---|
| 0.000001 mmHg | 0.00000133322 mbar |
| 0.001 mmHg | 0.00133322 mbar |
| 0.1 mmHg | 0.133322 mbar |
| 1 mmHg | 1.33322 mbar |
| 2 mmHg | 2.66644 mbar |
| 3 mmHg | 3.99966 mbar |
| 4 mmHg | 5.33288 mbar |
| 5 mmHg | 6.6661 mbar |
| 6 mmHg | 7.99932 mbar |
| 7 mmHg | 9.33254 mbar |
| 8 mmHg | 10.66576 mbar |
| 9 mmHg | 11.99898 mbar |
| 10 mmHg | 13.3322 mbar |
| 20 mmHg | 26.6644 mbar |
| 30 mmHg | 39.9966 mbar |
| 40 mmHg | 53.3288 mbar |
| 50 mmHg | 66.661 mbar |
| 100 mmHg | 133.322 mbar |
| 1000 mmHg | 1333.22 mbar |
| 10000 mmHg | 13332.2 mbar |
Engineering datasheets across Europe write millimeter of mercury to millibar several different ways. The calculation is the same in every one of them.
| Language | Written as | Unit names |
|---|---|---|
| French | mmHg en mbar | millimètre de mercure → millibar |
| Spanish | mmHg a mbar | milímetro de mercurio → milibar |
| Dutch | mmHg naar mbar | millimeter kwikdruk → millibar |
| German | mmHg in mbar | Millimeter Quecksilbersäule → Millibar |
| Polish | mmHg na mbar | milimetr słupa rtęci → milibar |
1 mmHg = 1.33322 mbar. One millimeter of mercury is the pressure exerted by a mercury column one millimeter high, which works out to 133.322 pascals.
Multiply the pressure in millimeters of mercury by 1.33322. For example, 50 mmHg × 1.33322 = 66.661 mbar.
Yes, exactly. One millibar and one hectopascal are both 100 pascals. Weather services relabelled millibars as hectopascals in the 1980s without changing a single reading, so a 1013 mbar chart and a 1013 hPa chart show identical pressure.
For practical purposes yes, but not by definition. A torr is exactly one seven-hundred-and-sixtieth of a standard atmosphere, while a millimeter of mercury is defined from mercury density and standard gravity. The two differ by about one part in seven million, which no clinical or vacuum gauge can resolve.
Multiply by 1.33322: 760 mmHg = 1013.2 mbar, which is standard atmospheric pressure at sea level.
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