Millimeters of mercury to atmospheres
Type a value in millimeters of mercury to see it in atmospheres straight away, or type in the second box to convert back.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the millimeters of mercury box.
- Read the result in atmospheres as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
atm = mmHg × 0.001315789661
Multiply the value in millimeters of mercury by 0.001315789661 to get atmospheres.
Example
To convert 25 mmHg to atmospheres: 25 × 0.001315789661 = 0.0328947 atm.
Conversion table
| Millimeters of mercury (mmHg) | Atmospheres (atm) |
|---|---|
| 1 | 0.00131579 |
| 2 | 0.00263158 |
| 3 | 0.00394737 |
| 5 | 0.00657895 |
| 10 | 0.0131579 |
| 20 | 0.0263158 |
| 25 | 0.0328947 |
| 50 | 0.0657895 |
| 100 | 0.131579 |
| 250 | 0.328947 |
| 500 | 0.657895 |
| 1,000 | 1.31579 |
About the units
- Millimeter of mercury
- The pressure of a 1 mm mercury column at the conventional density 13,595.1 kg/m³ and standard gravity: 133.322387415 Pa. Used for blood pressure.
- Atmosphere
- The standard atmosphere, defined as exactly 101,325 pascals.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many atmospheres are in one millimeter of mercury?
1 mmHg = 0.00131579 atm exactly.
How do I convert millimeters of mercury to atmospheres?
Use atm = mmHg × 0.001315789661. For example, 25 mmHg = 0.0328947 atm.
How many millimeters of mercury are in one atmosphere?
1 atm = 760 mmHg.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured from the surrounding air pressure, while absolute pressure starts from a perfect vacuum. These converters change the unit only, so a gauge reading stays a gauge reading.
Are torr and mmHg the same?
Almost. One torr is 101325/760 Pa, about 133.322368 Pa, and one conventional mmHg is 133.322387 Pa, a difference of less than one part per million. For everyday use you can treat them as equal.